It's for the editor to understand what parameters that are in play at the moment.
See, when using (string &in asParent, string &in asChild, int alState) it's about 1 entity (asParent) colliding with another entity (asChild), and how they are colliding (alState).
In your function you can then use if-statements like:
if(alState == -1)
{
//DO SOMETHING WHEN asPARENT WALKS OUT OF asCHILD
}
-1 equals that the function will only call if asParent walks out of asChild.
this might help you:
http://www.frictionalgames.com/forum/thread-18368.html
Trying is the first step to success.