Relationships
are a flexible way to combine data from many tables to do analysis in Tableau.
Relationship are called the logical layer meaning they keep the table separate and do not merge them into single table unlike joins .
They are noodle that connect related tables on the tableau data source page .
This video series below will explain :
1)Relationships in Tableau .
2)Business scenario in which we will be working on in this whole series of understanding Relationships in Tableau .
3)Data model Diagram and Relationship between tables.