what are the diffrences between" SAP r/3 GUI v 4.6c" and "SAP Front-End 6.4

daer friends i am new in SAP and i don't know exactly

the versions of SAP products plz if someone know

the versions of SAP plz write for me all of them and recent versions.

also i want to know what are the diffrences between" SAP r/3 GUI v 4.6c" and "SAP Front-End 6.4"