SQL commands are instructions used to communicate with database to perform specific task.you can create table, add data to tables,or modify data,drop table using sql command.
Data Definition Language (DDL) - These DDLcommands are used for creating, modifying, and dropping the structure of database objects. The commands are CREATE, ALTER, DROP, RENAME, and TRUNCATE.
Data Manipulation Language (DML) - These DML commands are used for storing, retrieving, modifying, and deleting data. These commands are SELECT, INSERT, UPDATE, and DELETE.
Transaction Control Language (TCL) - These TCL commands are used for managing changes affecting the data. These commands are COMMIT, ROLLBACK, and SAVEPOINT.
Data Control Language (DCL) - These DCL commands are used for providing security to database objects. These commands are GRANT and REVOKE.