Hi Linda,
The Mix and Match menu lets you select any exercise listed, perform that exercise, and then return to the Mix and Match menu. This differs from the Chapter menu in that you are returned to the menu; using the Chapter menu, you will select the exercise and then the DVD will continue to play from that point...
So, if you want to do the bicep hammer curls from a workout followed immediately by the core work from that workout, you would use the Mix and Match menu. If you just wanted to start you workout at the hammer curls segement and then continue on with the rest of the workout from that point, you would use the chapter menu.
If you want to program certain segments to play in a different order, and not have to return to the menu, you would want to use the Program feature that some DVD players have. That is explained in your DVD manual, but basically you have to figure out the title and chapter number of each segment you want to play, and then program those into your DVD player.
Hope that helps,
Wendy