A DBMS based on relational model is called relational database management system or RDBMS.
RDBMS uses relational structures to store data. A relation is also called a table.A relation contain tuples (rows) and attributes (columns).
In RDBMS tables are related each other.
Relation are set using a common column between tables.
In above tables, Roll_no is a common attribute between them which established a relation.