I have a basic table with 2 columns.
I have to create a query that shows the number of site each customer has. Can anyone help? I really have no idea what to put in the criteria.

eg.

Site No. Customer No.
1 1
2 1
3 1
4 2
5 3
6 3
7 4
8 5

You want to use the "count" aggregate function.

Go to the Help in Access, and do a search for "aggregate function" and you'll see it's pretty easy.