Lets talk about time. The timeline panel is one of the main things that separates After Effects from Photoshop. Unlike Photoshop, After Effects has the ability to make things happen across time. Another big difference between After Effects and Photoshop is 3D space. You can create compositions with 3D depth. After Effect movies are comprised of frames just like real films.

The Timeline lifespan

Think of the timeline like a lifespan—the beginning of the timeline's birth and at the end of your work area that's considered the death or the end of the lifespan.

Zoom into the timeline

You can zoom in on any point on the timeline with the button at the lower center of the timeline. Or you can zoom into your timeline by moving the slider. If you look closely you can you can see (F) for frames:

The timeline is measured with time codes. The F next to the numbers on the timeline stands for frames.