Rushhour is an example of a moving block puzzle. The pieces are cars and trucks in a garage. You can only move them forward or backward if there's space for moving. In each exercise you have to get your car (always the RED one) out of the garage, to the exit at the right side.
The exercise are sorted from simple to complex.
Drag the cars forward and backward to free places. With patience and smart plans and a bit of luck you'll finally succeed in getting the red car to the exit.
When you're stuck you can start again or ask the computer to calculate the shortest way out.