(You can also manipulate markers by right clicking on the time line or on a marker.)
Add Marker…
This lets you add a new time line marker.
Edit Marker/ Edit Nearest Marker…
This lets you edit the current marker or the nearest marker to your last click.
This launches the Marker Wizard dialog which lets you add multiple markers based on the silence in a sound or recording or at specific intervals. More on the Track Marker Wizard …
Play From Previous Marker
This causes playback to start from the previous marker based on the current playback time or last click position. You can also click Ctrl+Shift+[SPACE]
Play From Next Marker
This causes playback to start from the next marker based on the current playback time or the last click position. You can also click Ctrl+[SPACE]
Delete All Markers
This will delete all markers. (Note that the very first marker cannot be deleted.)