welcome to the site
gumpaste is like a clay that is used to mold figures, flowers, etc...it hardens very quickly and can be stored for a long time....i don't recommend eating it at all...you can do alot of things with gumpaste...when making a purse cake, some use it for the accessories of the purse (handles, zippers etc) you can mold cake toppers from gumpaste for any cake that you want...
some buy the ready-mix and others make their own
here is a link for the recipe from wilton:
i hope this helps a little bit