Marks are Bookmarks
Use Marks as placeholders in your movie where you can bookmark actions and change when you want them to appear.
Set Marks to be added automatically during the recording phase. You can also add Marks manually in the editing phase; in the timeline navigate the playhead to where you would like the Mark to appear, then click the + icon above the timeline, a menu will drop down where you can select what happens when the movie reaches the mark. When you have selected an action for your mark a dotted red line with a number at the bottom will appear in your timeline to represent the Mark. To remove a Mark, click on its number and click the - icon above the timeline.
Interactive objects, like click zones and buttons, will automatically add a mark to the timeline that stops the movie to wait for user interaction. Use Marks to automatically navigate to another Mark in the movie or send your viewer to a website.