Bruh when taken on its own means nothing, it is entirely dependant upon the context of a situation for meaning. It's similar to something like an exclamation mark, or using all caps in that way. Using it in a sentence, or even just on its own, typically adds some kind of emotion of confusion or disbelief to a statement. For instance, "what?" can have many meanings based on context, but saying "bruh what?" specifically implies that the cause for confusion was because the original statement itself made no sense.
"What is Obama's last name?"
"Bruh
"Bruh I got an A on that essay"
"Enjoy your meal"
"You too"
"Bruh"
It is a word commonly used to refer to a friend mostly towards a male, or an expression towards an illogical or horrendous situation, question, sentence, etc., it's use started around the early 20th century originating from the English word brother, used often by African American's slowly turning into 'brer' and 'brah' and now as 'bruh'.
E.g.,
Tommy: My bicycle was stolen so I had to take the subway and arrived late for class.
Charlie: Bruh.
When one of your bruhs is doing you dirty in a game without giving you too much shit talk but isn't holding back on you just because your friends. Could be used as a passive aggressive term when one friend is talking shit but another bruh who's better puts them in their place.
"We were playing Blazblue last night and Dias Bruh Dogged ForeverKnight all night."
"All Dias does is ledge guard in Smash." "Yeah man, hes just Bruh Doggin us every stock"
A stud that is a Lady & a Bruh at the same time. She gets hoes, but yet still loves the LORD. Name founded by Dnas & Young Shorty Doowop from the Bay. Yeeeeeee!