I am not sure if I understood the context of the question so let me rephrase . The TL wanted you to compare the application business flow and then verify if the tables required for this flow is present in the database by looking it up against the ER diagram ?

If this is the case you really need to know the business process and talk to the developers who implemented the tables to understand the design choices. If there is a logical and physical diagram available it might make things easier. Also if there is a design principles document you could refer to that as well. Proper naming conventions if they are implemented along with code comments within the procedures could also help understand a lot of whats going on.