BRB are the initials of "be right back", English expression that means "be right back", in the Portuguese translation.
This acronym is used especially in informal digital communications, like the chats and online social networks.
BRB (as the translation itself suggests) is used in the context in which a certain person is momentarily absent from a dialogue, but warning that he will soon return to continue the conversation.
Even though it is an English “slang”, BRB is used globally in the typical language of the Internet.
Several other acronyms are used in digital communications, such as sending SMS, on social networks or in messaging apps (Whatsapp, snapchat, vibe and etc).
Learn about the meaning of others common expressions on social media, like: LOL, LMFAO and OMG.
Unlike BRB, when one of the people interrupts the conversation and will take a while to return, it is customary to use the acronym BBL, which means "be back later" (or "I will be back later", in the literal translation into Portuguese).
O bulletin board ("be back in a second" or "I'll be back in a second", in the translation) is used to inform you that the pause in communication will be very fast.
There is also the GTG or G2G, which in English means "got to go" and it means "I have to go", or BCNU "be seeing you", which is translated as “up to sight”.
See also: the meaning of emojis.