It is a piece of paper/brochure, that is usually located somewhere right when you walk into the park. It has the date of the week as well as a list of all the events and times of things going on throughout the park.
As @Absolem mentioned, when you go into the park, you will see displays with both maps of the the park and a times guide that shows the timing for all the different events that week in the park. You can generally find both the maps and times guides in the parks by the cash registers in any of the shops also (because they know people lose them).
Here is an example of the times guide from Hollywood Studios used in a picture we used for the born in park badge.