intersection operator

I'm trying to understand the intersection operator in Excel. Can someone
tell me if the following is true. The intersection operator (the space
character) finds the intersection of two sets of cells not values. For
example, in the example below one cannot find the intersection of A1:A3 and
B1:B2 because the cells don't intersection even though the values do.

1 1
2 2

=SUM(A1:A3 B1:B2) equals #NULL!