The linking of a table occurrence to a layout will affect some of the related fields you can see from this layout. I quickly began to add the name of the table occurrence ( a code to it at least ) in my layout names, so that I can recognize any limitation the defined table occurrence may place on me. In general discussions, I've heard the relationship between a layout and a table occurrence referred to as a table context setting.
Here you can see where the table occurrence comes into play in the layout setup dialog box. This pull down menu highlighted ( Show records from ) will show you all the defined table occurrences and you pick one to link to the layout.
Here you can see the defined table occurrences for the FileMaker file I’m working on. You can see how some of the base tables appear more than once but have different names. This is because how they are used on the relational graph.