It is used as a name for someone you love, your friends, or your homie.
"Hey wassup B, how are you"
"Love you B."
"You good B?"
n. (bēē) Pronoun implying friendship, used for siblings, friends, significant others.
Whats up, b?
specifically lowercase b looks like a thumbsup
A: Nice, I managed to get some good loot from this boss I've been grinding!
B: b