Roughly speaking, the three points include:
1. making a mark-in point from preview window
2. making a mark-out point from preview window
3. selecting a point to insert the clip into the timelime
- the first two points define either THE IN AND OUT POINTS IN THE SOURCE MEDIA or the IN AND OUT POINTS IN THE TIMELINE
- the third point indicates indicates either the IN OR OUT POINTS IN THE SOURCE MEDIA (If the other two points are in the timeline or the IN OR OUT POINT IN THE TIMELINE (if the other two points are in the source media)
