Definition of bvb
Bvb is the written form of blind versus blind. If you want to write down a hand that you played and you were small blind versus big blind, you would say that the hand was played "bvb". At the poker table, the most common hands are those played with the bilnds. You will most often play with the players immediately to your left or right. This is especially true in tournaments when the blinds are huge. When all the players in front of the button fold, the button often takes advantage of this to raise. The players in the blinds then go into defensive mode. If the button folds, it will be a bvb hand.
The particularity of a bvb hand
In a hand played bvb, the hand ranges will be smaller (larger range). If a player raises UTG and the big blind calls, we know that the UTG player does not have J5 or Q5. In a bvb situation, it is possible that he does. Solvers in recent years have taught us that when the action is folded to the small blind, you have to be much more aggressive than players were back then. Today's players play many more hands from the small blind and the big blind, which sometimes makes for epic battles. Hands in a bvb situation are harder to read than if it were UTG vs BB for example.