I was looking at pictures of scoreboards today, and I noticed that some of them have 'B's on the boards:
The same thing appears on NBA games, often in the broadcast scoreboard as well:
I've never noticed those before. What do they mean?
That's a bonus marker.
A team who commits 7 fouls gives the other team a bonus - which gives a free throw with every foul from that point on.
The second B on the second image indicate that a team has reached 10 fouls (in HS and college this is the double bonus and means that you shoot 2 foul shots from there forward instead of 1 and 1)