Generated Structures are randomly-generated features found throughout a Minecraft world. Generated structures can be found in many Biomes, alternate dimensions, and can be either natural or manmade features. Some of these Stuctures can be found by doing the /locate command.
The Overworld is home to many different generated structures. The following is a list of most of them, in alphabetical order.
Abandoned Mineshafts are large, complex underground tunnels that contain wood, rails, and minecarts filled with loot. In some cases, cave spider Mob Spawners can be found encased within a cluster of cobwebs. Some other Mob Spawners that are possible too find are Zombie and Skeleton. A mineshaft is a good place to find ores, considering that is probably what the mineshaft was originally used for. They frequently connect to a dungeon.
Dungeons are small 5x5 (sometimes 7x7) rooms, that randomly generate underground, usually near an abandoned mineshaft or cave. Dungeons contain a mob spawner, which will spawn either Zombies or Skeletons, as well as two loot chests filled with random items, including some that are not craftable (such as a lead, saddle, or name tag).
IglooIgloos randomly generate in Ice Plains Biomes and Cold Taiga Biomes. They are very small and simple, and contain a bed, crafting table, furnace, and a redstone torch. Occasionally, breaking one of the carpets will reveal a ladder down to a basement. There is villager next to a zombie villager, both in separate cells. A chest nearby contains a golden apple and other assorted loot, and a brewing stand nearby contains a Splash Potion of Weakness. In which you can use these items to turn the Zombie Villager into a Villager.
Terrain varies throughout the overworld, depending on the biome and world generator. Players can find hills, mountains, caves, ravines and many other natural structures. Tree species and other natural structures like Huge Mushrooms also vary (or may not generate at all), depending on the biome. There is always a chance that a world seed will generate an overworld containing extreme or unusual terrain.
Ocean Monuments are underwater, pyramid-like structures, which randomly generate in Ocean Biomes. They consist of several types of rooms and hallways, and are populated with Guardians and Elder Guardians. This is the only place in Minecraft where one can obtain a Sponge.
Players can find two different types of temples in two different biomes throughout the overworld. They are similar, since both contain loot and traps.
Desert Temples are found in Desert Biomes. They are pyramid-shaped, and made of sandstone and colored clay. If a player manages to safely reach the bottom of the hidden loot room, without stepping on the pressure plate, they can retrieve treasure out of four chests (with one usually containing a Notch Apple). If a player steps on the pressure plate, it sets off TNT, which destroys all of the treasure.
Jungle Temples are found in Jungle Biomes, and are normally hidden within dense tree growth. The temple itself is made of mossy cobblestone and is covered in vines. Two chests of loot can be found inside. In order to reach them, the player must safely make their way through a tripwire and dispenser-filled corridor.
VillageVillages consist of several different buildings, populated with various types of Villagers, and sometimes an Iron Golem. A village's appearance and layout varies based on the biome in which it generates. For example, a village that is generated within the desert will have houses built of sandstone, instead of wood. Certain buildings within a village may or may not spawn, such as the tall cobblestone "church" or blacksmith building.
Woodland Mansions generate in the Roofed Forest Biome. These structures contain hostile Vindicator and Evoker mobs, as well as multiple loot chests. This is the only structure that a player can get a Totem of Undying.