Use composition markers and layer markers to store comments and other metadata and mark important times in a composition or layer. Composition markers appear in the time ruler for the composition, whereas layer markers each appear on the duration bar of a specific layer. Both kinds of markers can hold the same information.
Markers can refer to a single point in time or to a duration.
Composition markers in After Effects correspond to sequence markers in Adobe Premiere Pro. Layer markers in After Effects correspond to clip markers in Adobe Premiere Pro.
When you render a composition that contains markers, the markers can be converted to web links, chapter links (chapter points), or cue points, depending on the output format and values that you set in the marker dialog box. Markers can also be exported as XMP metadata. (See XMP metadata.)
The default comment for a composition marker is a number, whereas the default comment for a layer marker is nothing.
A marker that contains link or cue point data has a small dot in its icon.