When you obtain a FastPass ticket, you will be given a one hour time in which to enjoy the ride. For instance, your FastPass ticket may say 11am to 12pm. This means that you can show up and move to the front of the line between the hours of 11am and 12pm. You must have your Disneyland ticket in order to obtain a FastPass ticket.
At Disneyland, FastPasses are available for Indiana Jones, Splash Mountain, Big Thunder Mountain Railroad, Roger Rabbits Cartoon Spin, Autopia, Space Mountain, and Buzz Lightyear.