PowerPoint executes all the animations as sequence of events. Any object (text/image/shape) can be made appear, fly in as a result of click or after effect of some action. Any action for example a click results in next animation or slide.
You can't just jump on to a particular event of your choice or repeat an action again and again. For example what if you want to stay on same slide and display an image again and again on click on a text say "Who is founder of Microsoft". In such scenarios where you have to bypass sequencing or repeat actions while staying on the same slide, PowerPoint triggers is the best option available. Triggers can only be set on some animation effect.
- Select any text/object, apply some custom animation effect.
- Either double click or right click the animation effect applied(on custom animation sidebar).
- Click on 'timings' tab, click Triggers button and select the radio button "Start effect on click of".
- Select the event on whose click you want selected animation to execute.
Video triggers in PowerPoint 2010PowerPoint 2010 offers Video Triggers; a feature with which one can mark locations in a video (i.e. set bookmarks), and then trigger animation sequences upon reaching those bookmarks on playback of the video. In simple terms you can set some specific animation to run when a particular scene appears in video inserted in PowerPoint.
Image via Microsoft PowerPoint Blog