an injector is a programe that injects an hack (an .DLL) normaly some sort of aimbot or some sort of hack that has a menu
you load up the injector, and you choose what to inject into, EG Engine.exe(combat arms)
you then tell it wat to inject, blahblah.DLL (an wall hack maybe)
then you tell it to inject, open combat arms and it'll auto inject.
basicly an injector is the base of hacks (ATM)