Brenda,

Your WHERE clause is doing what is called either an inner join or a simple join. The best way to understand the four types of joins is to use sample data;

Table1
OwnerID         Owner Name
1               Smith
2               Jones
3               Miller

Recordings
RecordID         Owner ID
1001              1
1002              2
1003

Notice that Recording 1003 has no owner and owner 3 has owns no recordings.

Here are the joins;

Inner Join (or Simple Join)
Owner         Recording
Smith            1001
Jones            1002

Left Outer Join
Smith            1001
Jones            1002
Miller

Right Outer Join
Smith            1001
Jones            1002
                 1003

Full Outer Join
Smith            1001
Jones            1002
Miller           
                 1003

Cartesian Product
Smith            1001
Smith            1002
Smith            1003
Jones            1001
Jones            1002
Jones            1003
Miller           1001
Miller           1002
Miller           1003

Hope this helps.