what is a crypto bridge?

[cafter]

I don't know this is a write board to ask this questions or not..

what is crypto bridge? google search results shows it connects two blockchains despite the fact that both blockchains may have different protocols, governance models or rules.
how it's work does it works on bitcoin? is it done on bitcoin anytime?

Edit: I think it's like an exchanger but from other blockchains? And this question is about altcoins? moving this thread to trash/archieve