What is Kants kategorical imperative?

Kant's kategorical imperative is a maxim - a rule - which states that all your actions must be such that they could creature the foundation for a law about how everyone ought to act in similar situations. In other words, remember when your mother told you're not allowed to litter, because the town would look horrible if everyone did that? In her own way she was saying your actions didn't live up to Kant's categorical imperative.