Power shield tutorial needed

Is there a tutorial for power shields that is reasonably technical? I am trying to understand an existing project using the Velleman KA03 shield to teach me how motor shields work. In particular, how do the row of connectors Pin Select work? In the attached picture, why are pins 2 and 3 jumpered to the pins opposite them? Also, why are the two blocks of connectors wired together at the bottom, as shown in red and orange?

The project I am looking at is:

Unfortunately, the sound does not work on my PC.

Thanks in advance