Good evening Ahmed
Extra: have a lot of meaning
Extra can be adjective, a noun or an adverb
Advective : mean beyond what is due
Ex: he need extra time to finish
Noun : something additional
Ex: he carried extras in case of something happened
Adverb : mean an extraordinary degree
Ex: loòook , it's an extra fast car
-we can use it as a slang like if your friend is laughing hard at your jok by unnatural way you can say " he's extra "
I hope i could explain it in a good way