Creep

A creep is the main unit of Screeps. They are created from spawns and have bodies made of several different parts up to a total of 50. The configuration is entirely up to the user as long as enough energy is available in the room to spawn them. Their role in a colony is entirely dependent on the user, as beyond the body giving different abilities to creep, there is no predefined role for any given configuration.

You can learn more about creeps by visiting its API page or Docs page