Working with related tables and files > About the types of relationships
 
About the types of relationships
When you join two tables using a relationship, you establish criteria that FileMaker Pro uses to display or access related records.
Your criteria can be simple, such as matching a field in TableA with a field in TableB. A more complex relationship definition will usually return a narrower set of related records. Examples of complex relationships include using multiple match fields, comparing match fields using non-equal relational operators, or using calculated match fields.
Related topics 
About the relationships graph
About match fields for relationships
Creating and changing relationships