I know that the open subsets in the product topology of $X=X_1\times X_2\times...\times X_3$, where $X_1,X_2,...,X_n$ topological spaces, are the union of subsets of X: $U_1\times U_2\times ...\times U_n$, where $U_1,U_2,...,U_n$ are open subsets of $X_1,X_2,...,X_n$ respectively.
I have a question, how the closed subsets look like? can I say that they are the union of the subsets of X: $F_1\times F_2 \times...\times F_n$, where $F_1,F_2,...,F_n$ are closed subsets of $X_1, X_2,..., X_n$ respectively? In fact, what they are?
thanks