Creepers are hostile mobs that makes use of a suicide-style attack: It approaches players and then explodes, causing damage to players as well as surrounding blocks and entities. Creepers spawn in the overworld at night, and in locations with a light level of 7 or less, just like most other hostile mobs; however, unlike Zombies and Skeletons, Creepers will not catch fire in direct sunlight, and those spawned in darkness will nevertheless continue wandering and attacking throughout the day in any physically accessible area until they are killed or despawn.
Creepers are especially dangerous mobs due to their near-silent approach, save for light footsteps and a signature 'burning fuse' hissing noise that often signifies it's already too late. Their explosion is devastating at short range, to both entities and structures.
Creepers run from cats and ocelots, and will even ignore the player to run away when a feline is too close. As cats can be acquired and controlled by the player, this provides an important avenue of defense from Creeper attacks.
Creepers have gained notoriety and infamy among Minecraft players for their infuriating habit of sneaking up on the Player to inflict devastating damage following an all-too-short warning sound. They have arguably become the most recognizable image from Minecraft, as well as the game's unofficial mascot.
You can find this in the Minecraft wiki Article
Edward: ugh... I hate how a Creeper suddenly explodes in your face.
Logan: Yeah, that sucks.