A database is an organized collection of data.
DBMS refers to the Database Management System. It is a set of programs that enables you to store, modify, and retrieve the data from a database.
RDBMS refers to the Relational Database Management System. It is a database management system that is based on the relational model as introduced by E. F. Codd. All modern database systems like MS SQL Server, Oracle, IBM DB2, MySQL, and Microsoft Access are based on RDBMS.
Difference between DBMS and RDBMS: