The phrase "we chill" is generally used in reference to the state of two parties or people being in a state of "chill", "cool" or "non-hostility" towards each other. For example;
Party 1: "Yo, weren't we gonna have that arms race tomorrow?"
Party 2: "I mean, we don't really care much, we chill?"
Party 1: "Sure, we chill."
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.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"