Press Cmd-7 to open the Timeline tab.

The Layer list includes one layer with four objects. How can you tell? You can count the blue object regions (clips) in the Timeline, or just look at the lower-left area of the Layer region in the Timeline; Motion always shows you how many objects are within a layer. In this case, Motion displays 4 Objects. If you look below the Layer object in the Layer list, you'll see a text object, two still-image objects, and one video object.

Just like the Layer list on the Layers tab, the Layer list on the Timeline tab includes buttons to enable behaviors and filters, and activation boxes to turn elements on and off.

Let's move the playhead to the beginning of the project and look at the elements in the Layer list a little more closely.

Press the Home key to move the playhead to the first frame of the project.

On the Timeline, the playhead is over two objects (blue regions): detonator_stealth_trans and surf_1_SD_jpg.

Notice that these objects have colored icons on the Layer list. Whenever the playhead is over an element in the Timeline, the icons for those elements appear in color in the Layer list. This is also true for the Layer list on the Layers tab.

Let's test this by moving the playhead farther into the project.

Type 2.20 in the Current Frame field and press Return to move the playhead forward to 2;20 in the Timeline.

The playhead is over all four objects in the Timeline, and all of their icons appear in color in the Layer list.