Right, short and sweet: What is a ripkit, what does it do, and why can't you just use DUMD Dumper to do all the ripping, why a different one for each game?

Ripkits make the games smaller so they take up less space on the memory card.
They remove any padding and unnecessary files such as audio for other languages, videos, the update firmware folder, etc.
The UMD dumper, as its name says, dumps the UMD to a .iso file, then a ripkit will make the .iso file smaller.