Minecraft is home to a variety of unique and vast terrain expanses known as "biomes", sets of geographical locations that can be identified as the region you're currently in. Minecraft has a ton of these, so we'll go over them in minor detail to help you orient yourself when exploring.
Overworld
Plains Biomes
A set of biomes mainly comprised of flat terrain and few obstructions.
Plains
Simple but elegant, the Plains are flatlands with few trees and lots of grass. A staple of Minecraft, and an excellent place for a home.
Sunflower Plains
Like normal Plains, but with Sunflowers. This is the only location in which sunflowers grow. Be sure to collect some for decoration!
Savanna
Home of the Acasia tree, Savannas are arid lands with tall grass and somewhat flat topography.
Snowy Plains
Plains with snow. Comes with rabbits, polar bears, igloos, and did I mention snow?
Ice Spikes
A variant of the Snowy Plains biome, the Ice Spikes biome is filled with, you guessed it, pillars of ice resembling a bunch of spikes.
Arid Areas
Coarse, rough, and it gets everywhere... Yep, it's sand.
Desert
Home of the Desert Temples, deserts are full of sand, cacti, and dead bushes. Water is somewhat scarce here, so if you need some, you're likely in the wrong place.
Badlands
A variant of the Desert, Badlands are filled with Red Sand and Terracotta.
Wooded Badlands
A Badlands variant, this biome contains an abundance of terracotta, coarse dirt, and oak trees.
Eroded Badlands
Another Badlands variant, this time with large Terracotta spires scattered about.
Beach
Where the ocean meets land, Beaches are typically found as sandy areas touching large bodies of water. You can find treasure and turtles here. Get digging!
Snowy Beach
Much like a normal beach, but with snow and land that meets with a Frozen Ocean. No turtles to be found here.
Forest Biomes
Trees, trees, and more trees. It's a perfect place to gather wood of all types.
Forest
A typical, heavily wooded area filled with birch and oak trees as far as the eye can see. Also a great area to find Wolves to tame!
Birch Forest
A variation of the Forest biome with only Birch trees and a lack of wolves.
Old Growth Birch Forest
A Birch Forest biome with much taller Birch trees, useful if you're looking for even more Birch than normal.
Dark Forest
A Forest variation filled with Dark Oak. The densely packed trees may blot out the sunlight enough to allow hostile mobs to spawn even during the daylight. Stay alert!
Flower Forest
Another Forest variant, which replaces a majority of trees with patches of various flowers. Useful if you're hunting for dyes or decorative flora.
Taiga
The Taiga biome is a forested area filled with ferns and spruce trees, and inhabited by foxes and rabbits. It's also a great place to find berries!
Snowy Taiga
A snowy variant of the Taiga biome with a majority of the same features.
Old Growth Spruce Taiga
Another variation of the Taiga, this time with thicker spruce trees and significantly more leaves. Check for trees covered completely in leaves!
Old Growth Pine Taiga
Yet another variation of the Taiga, Pine Taigas possess skyscraping spruce trees. This biome also possesses cobblestone and podzol, if either of those interest you!
Jungle
Welcome to the jungle, literally. This biome is packed with jungle trees thick and thin, tall and short, most of which are covered in vines. Jungles are home to Cocoa plants, of which you can harvest and plant elsewhere.
Sparce Jungle
A Jungle, but with far less trees, leaving it much less dense and easier to traverse compared to its original counterpart.
Bamboo Jungle
A jungle where the Bamboo reaches as high as the trees, and a natural playground for Pandas.
Grove
Groves are essentially packets of spruce trees and snow that spawn near or on the base of mountains. Visually, it's very similar to a Snowy Taiga.
Cherry Grove
Cherry Groves are home to the Cherry Tree, identified by their pretty pink leaves. Another great find for those looking to decorate their homes
Pale Garden
An ash grey land that, when night falls, you'll constantly feel like you're being watched. And you are. Only hostile mobs spawn within the Pale Garden, most prominently being the Creaking. You can find more about the biome here, and about the Creaking here.
Swamp
Home of Frogs and Witches, Swamps are filled with lilypads and shallow waters, along with trees and darker colored grass. Easily identifiable due to the greyish water tint.
Mangrove Swamp
A denser Swamp with Mangrove Trees and a lot of mud. Difficult to navigate through,
Mountain Biomes
For those who think sea level is suffocating.
Jagged Peaks
The daggers of the sky, the Jagged Peaks biome is a mountain filled with rocky spikes reaching past the clouds. Jagged Peaks are rich in ores, including emeralds. Finding the treasure at such an altitude carries risk, so use caution.
Stony Peaks
Part of warmer biomes, Stony Peaks are generated with no snow upon its peak, leading to somewhat easier access to the ores on top of the mountain. Useful for those looking for quick materials without cave-diving.
Frozen Peaks
While not as spiky as the Jagged Peaks, Frozen Peaks still reach high into the sky and are densely packed with ice and snow.
Snowy Slopes
Mountains covered in both snow and powdered snow, Snowy Slopes are home to both goats and rabbits. Igloos also spawn in these biomes. Be careful, powdered snow is a falling hazard, so watch your step!
Windswept Hills
The Windswept Hills are a bit of a wacky biome with extremely steep cliffs and valleys, making for trecherous traversal. Floating islands are also somewhat common. This biome also holds an abundance of ores and also can come with emeralds. And Llamas. Llamas are good too.
Windswept Savannah
A Savannah within the mountains, expect similar features from both the Savannah biome and the Windswept Hills biome packaged neatly into a mountain.
Windswept Gravelly Hills
Much like the Windswept Hill biome, but with a bunch of Gravel. Watch out for falling gravel!
Meadow
A grassy mountainside with an abundance of flowers. Also a great place for the botanists, or those looking for a bit more dye. Trees in Meadows always spawn with a beehive!
Savannah Plateau
A Savannah Biome, but at a higher altitude. Generates within mountainous regions.
Stony Shores
Much like a beach, but spawns on the sides of mountains that touch the ocean. No turtles here, just a bunch of stone and treasure if you're lucky.
River
Characterized as water flowing between stretches of land, rivers are host to squid and salmon, but also to drowned. Follow it and it may lead you to an Ocean.
Frozen River
Similar to a normal river, but with a layer of ice.
Ocean
Large, expansive bodies of water. Rich in sea-foilage such as kelp and seagrass, and inhabited by multiple types of fish.
Deep Ocean(s)
Deep Oceans are just variants of Oceans with a much lower seafloor. A deep variant exists for all Ocean biomes, but the only real change is the depth. Bring enchanted gear or water breathing potions if you wanna go to the bottom!
Cold Ocean
An Ocean with a deeper blue color and less fish, but with more kelp.
Frozen Ocean
Ocean of the icy variety, comes equipped with squid, salmon, an occasional polar bear, and ocean monuments.
Lukewarm Ocean
On the opposite end of the Cold Ocean, the Lukewarm Ocean is a biome with a slightly lighter tint of blue, and is home to a larger abundance of salmon, cod, and kelp.
Warm Ocean
Even brighter than the Lukewarm Ocean, the Warm Ocean is home to Coral Reefs and Dolphins, as well as a greater variety of tropical fish.
The Nether
Nether Wastes
Large expanses of Netherack and Lava, the Nether Wastes are one of the most common areas within the dimension. It is home to Nether Gold and Nether Quartz, as well as Piglins and other hostile entities. You'll be around these areas a lot, so be sure to learn its quirks quickly while exploring.
Basalt Deltas
An ashy Biome filled with pillars of Basalt and Lava, this area is particularly dangerous to navigate, as wrong footing may end up costing you an uncommanded swan dive into the unfriendly lava below. It also spawns Magma Cubes and Ghasts to further add to the danger. If you listen, you'll hear a Geiger Counter ticking every now and then.
Soul Sand Valley
As the name suggests, the Soul Sand Valley is an area encompassed by Soul Sand and Soul Soil. You'll also find fossils, minor structures of bone blocks that can help feed the average botanist's Bonemeal addiction.
Crimson Forest
As the name suggests, the Crimson Forest is filled with Crimson colored fauna, and are home to Hoglins. A nice place if you're looking for a little red for your home, or a source of wood within the Nether.
Warped Forest
Much like a Crimson Forest, the Warped Forest is a tourquise colored biome within the Nether that provides a decent amount of wood for your crafting or building endeavors. Unlike Crimson Forests, or any biome within the Nether, Warped Forests only spawn endermen as mobs, making it a safe haven within the Nether if you're looking to find a new home.
The End
The End
No, that wasn't a typo. The End Biome is the main area in which you will fight the Ender Dragon, consisting of ten pillars topped with End Crystals with an Exit Platform at the center constructed of Bedrock. This is the only End biome within Bedrock editions of Minecraft.
End Highlands (Java Only)
The End Highlands are the only current End Biome that can spawn the Chorus Tree, purple growths that can hold Chorus Fruit, the only natural edible source of food within the End. It also may generate with an End City, as shown above. Highlands typically have elevated terrain, as expected from the name.
End Midlands (Java Only)
Absent of Chorus Trees, the Midlands are rough terrained expanses. End cities may also generate here, but you won't find Chorus Trees till you get to a new Highlands area.
Small End Islands (Java Only)
Small, circular, barren platforms of Endstone. Nothing for you here apart from the occasional mob.
End Barrens (Java Only)
The edges of Midlands and Highlands, Barrens are essentially the end of each biome, and the entrance to the void below. Be careful not to fall, as if you don't find something solid, you're in for one lengthy, terrible tumble.