the tables in FileMaker could be much the same they are in Access. One important thing you should understand in FileMaker is the difference between a Table and a Table Occurrence.
The table is the container that holds the data (same as Access).
The Table Occurrence, that you find in the Relationship Diagram is the representation of a Table. For someone with an Access background, this is how I explain it:
think about creating a query in Access. You can directly create the SQL Query by typing 'SELECT column1 FROM Tablex...' Or you can create it graphically by dragging tables and linking fields for the WHERE. The Table Occurrence are the same.
In FileMaker, you can't define relations at the Tables level, only at the Layout (Form) level. This is why a Layout is always linked to a TO.
Sounds like you need a conditional menu. Conditional menus are based on relationships so you can displays a subset of values in a popup menu rather than all of them. Attached is an example of the Value List dialog with a conditional menu specified.