The best way to learn is to go on line and look at a manufacture's web site - I recommend Bushmaster's as they sell everything on your list.

A1 - carry handle, 3/4" shorter stock, simpler rear sight.

A2 - carry handle, 3/4" longer stock, rear sight adjustable for windage and elevation.

A3/A4 - flat top.

Vmax - Olympic Arms flat top name

Dissapator/Elemanator/*.ator - shorter carbine barrel with longer rifle hand guard

H-Bar - heavy barrel

Match - cut with a smaller chamber which will give you more accuracy and less reliability

AK Shorty - Bushmaster rifle with 14.5" heavy barrel and an AK brake