In Chapter 7, you learned that a relationship graph doesn't really depict tables—it shows table occurrences (also known as TOs). They're just graphical representations of the underlying table. Because these occurrences are representations, you can make new occurrences of a table without duplicating it (and all its data). FileMaker's not trying to confuse you; it's actually helping you relate to the same table in different ways.
When you create a very simple database, you have only one table occurrence on the graph for each table, so it's tempting to think of them as the tables themselves. But as you add new and more powerful features to your databases—and the relationships to make them work—sooner or later you'll need to graph the same table multiple times so you can keep everything straight.
Few databases can manage all their tasks without multiple occurrences of the same table. Your Customers database is no exception. Here's an example: Your database has expenses to record what you buy to service your customers. It also has line items to record what you charge your customers for. Right now these are connected only by way of jobs. Figure 8-11 illustrates how your tables are currently related.