HYPOCRITEs

Hey been a while, how have we been?
Got something bothering me and I wanna ask us.
Can someone please explain the meaning of ASS LICKING/LICKER to me.
I see lots of persons calling people ASSLICKERS yet they do worst to those they are loyal to.
I just wanna know if there's another meaning of ASS LICKING/LICKER, or is it that they are ignorance of the meaning ASS LICKING/LICKER?
Or they are just being an HYPOCRITES?
Please opinions are needed thank you.