Cats sleep.

Meaning: This means that cats are in a state of rest in which their bodies and minds are not active. It's like saying, Cats are not awake and are not moving.

Choice of Words: Cats are small, carnivorous mammals that are often kept as pets. The verb sleep means to be in a state of rest in which the body and mind are not active. When you put them together, "Cats sleep" is a statement that describes the state of rest that cats enter when they are not active.