Creepers are explosive creatures from the Minecraft Universe. It is highly dangerous and is claimed as one of the most dangerous mobs. If you go near it about 16 blocks, it will look at you, come towards you then explode on you. They can destroy your house and all the stuff in it. Be wary of creepers if you play on survival mode and your difficulty is set on easy - hard because they will spawn at night and never burn in daylight. If that's not enough for you, there's a more dangerous creeper called the Charged Creeper. This can happen only when a creeper get struck by lightning. It has an explosion radius 2 times more than normal creepers. If you want to survive these guys, remember, do NOT put your house in a place in grasslands because they are hard to spot due to their green color.
They have been hinted by the game's creator, Notch, as sounding like crunchy dry leaves when they move, and using knowledge of biology, the popular YouTube channel "Game Theory" has shown that are very likely to have evolved from peat moss.