Derma Skin Hooks?

I’m trying to make my own Derma skin, doing well so far, but I have one question:
Why are there five hooks for each element?

 Draw <Element Name>
 Layout <Element Name>
 Paint <Element Name>
 PaintOver <Element Name>
 Scheme <Element Name>

Are you supposed to use certain ones for different things, or does it matter?

Don’t know about draw but,

Layout is when the panel organizes it’s children
Paint is when it draws
PaintOver is when it draws something which will paint over the Paint hook
Scheme is when a base VGui element (TextEntry) is modified for use with Derma

The wiki documentation is very poor for derma skins.

I’ll run a bot to dump all the functions to the wiki later.