If $A_i$ is a set, what does $\bigcap^n_{i=1} A_i$ mean?

Question

If $A_i$ is a set, what does $\bigcap^n_{i=1} A_i$ mean? I'm not sure what the upper and lower bounds on the intersection symbol means.

Answer 1

It means$$A_1\cap A_2\cap\ldots\cap A_n.$$In other words, it's the intersection of the sets $A_1,A_2,\ldots,A_n$.