A board on 4chan. I recommend you not going on it, because 90% of the time on the very first page, there will be images of either naked fat guys, nude grandmas, penises or dead people. Please, don't damage your mind with /b/.
This is obviously a the second letter of the alphabet, but in the hood the term " B" represents an alternative word for bro or homie
The slang term "B" is a term mostly used up to today in the streets of Harlem New York City