A kitten is a baby cat. There is nothing more adorable then a bunch of fuzzy little kittens playing together.
While there are a few other animals whose young are called kittens, like beavers, rabbits, and rats, the word most commonly describes a baby cat. Kittens are dependent on their mothers for food and protection until they are around six to eight weeks old, when they're still adorable but also able to eat solid food. Kitten comes from the Middle English kitoun, which is rooted in the Old French chitoun, or "little cat."