Well, I suppose
- $m stands for mode or maybe module. It is used by those switches to detect which mode of the script to use.
- $n is like $m, but is more generic. In forums it is used to specify special paging modes (or numbers): n=last means go to the last page available.
- $a means action. For example 'update', 'send', 'add', etc.
- $b is the next latter after $a, isn't it? So it is similar, but more generic.
May the Source be with you!
