The In / Out Point controls are a part of the Playback settings.
What is the In Point
The In Point is the position in the media where playback will start from.
For example, if you set the In Point of a movie to 2 seconds, then whenever the movie starts to play (or loops back to the "start"), it will start from 2 seconds into the movie.
What is the Out Point
The Out Point is the position in the media where playback will end.
For example, if you set the Out Point of a movie to 2 minutes, then whenever the movie gets to the 2 minute mark, it will loop or stop playing (depending on the When Finished options you have set.
An Example
Imagine you have set the In Point to 5 Minutes and the Out Point to 7 Minutes and set When Finished to "Loop".
In this case, then when the movie first becomes Live, it will start playing from the 5 minute mark in the movie.
It will continue to play until it hits the 7 minute mark (it will have played for 2 minutes).
Then it will perform the Loop action, and return back to the 5 minute mark and start playing again.
You would move the playhead to a place you want the media to start, and then press the "Set" button to set the In point to that point. See In and Out Points for more information.
Setting the In Point
To set the In Point, you have to move the playhead to the point in the media you wish the In Point to be.
Then you press the first Set button, as shown above.
Setting the Out Point
To set the Out Point, you have to move the playhead to the point in the media you wish the Out Point to be.
Then you press the second Set button, as shown above.
Jump
Pressing the Jump button will move the playhead to the In Point or Out Point.
Time Strings
Both the In Point and Out Point show the time which the point represents.
In the example shown above, the In Point is at 5 minutes and 20 seconds into the movie. The Out Point is at 1 hour, 39 minutes and 5 seconds.