the basic data structure of the relational model is the table, where information about a particular entity (say, an employee) is represented in rows (also called tuples) and columns. thus, the "relation" in "relational database" refers to the various tables in the database; a relation is a set of tuples. the columns enumerate the various attributes of the entity (the employee's name, address or phone number, for example), and a row is an actual instance of the entity (a specific employee) that is represented by the relation. as a result, each tuple of the employee table represents various attributes of a single employee.