openning kill = Holding an angle as a T and waiting for CT if they push, get a frag.
Entry kill = Being 1st while rushing, getting kill
Its literally that easy. Bottom line is, oppening kill is consider 1st kill of the round. That kill counts even if T's are camping spawn and CT's push and they get a kill. Entry frag is being 1st while rushing a part of the map and getting a kill. Something that zywoo does 1 in 20 rounds. Its ok cuz its not his role.