From Minecraft Wiki
Mushroom may refer to:
Mushrooms - naturally occurring types of fungus that are commonly found in dark places. There are red and brown variants, and one of each type plus a bowl can be crafted into mushroom stew.
Mushroom (block) - a solid block that is part of huge mushrooms.
Mushroom Stew - a food item created from small brown and red mushrooms. Mushroom stew was one of the more filling foodstuffs available in the game.
Huge mushroom - giant variants of the small red and brown mushrooms.
Mushroom island - a biome made up of mycelium blocks and filled with mushroom-related objects.
Mooshroom - a cow 'infected' with red mushrooms which only spawns in mushroom biomes. It is red, can be sheared for mushrooms, can be 'milked' with a bowl to gain mushroom stew, and can be milked with a bucket to get milk.
Nether wart - a mushroom like plant found naturally in the nether.