Simply stated: Reinforcement Learning deals with actions and rewards (positive or negative). The rewards help to dictate the future actions.
Many children learn via reinforcement learning. Here is a simple example from my childhood. As a child, I was told not to touch the hot stove.
My action: I touched the door of the hot stove when it was open.
My reward (negative): I burned my hand, and it hurt.
My future actions resulted in me staying away from the hot stove.
This was a very simplified example of reinforcement learning. Here are two more great introductory references: