-Can be used as a greeting.
-Another way to say goodbye, correct, okay, sounds good, etc.
-The only words uttered between bros (must be yelled).
(Pretty much can be said to answer anything)
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.