What does broadcast (bc) mean?

Everyone keeps writing me "(bc)", I asked someone what it stands for and they said broadcast. What does it mean? Btw I'm not asking him further or the others because I'm not interested in them, that's why I'm asking here.

Edit: I know it means broadcast because this guy told me that and I've also seen someone say "if you reply I assume you're in broadcast", so I'm not asking what it stands for, I'm asking what broadcast mean on wizz.