Help with Bayes's theory

Question

I know how to use this form of the Bayes's theory :

$P(A | B) = P(A ∩ B)/ P(B)$

But how do I use?:

$P (A | B,C) = P (B | A,C) P(A | C)/ P(B | C)$

What does the comma mean?
I know its a simple question but I really need to know the answer.

Answer 1

The comma usually means "and" so P(A|B,C) is "probability that A happens given that B and C happens"