In QuickTime, you can have as many samples as you would like inside of a track. To better understand the different tracks of QuickTime, we must first look at their purposes. Each different type of track has a different purpose, or different type of media samples it can contain. A sprite track is a visual track. It stores samples that are displayed on the screen to the user.
Sprites can be interactive in many ways.
In fact, the things sprites can do are almost infinite. They are also capable of animation. These images are static and cannot be animated. The picture track is often used as a background image or for slide shows. Effect samples call on specific effects to be rendered on the end user's machine at certain points in time.