Majorly SQL commands can be divided into three categories, i.e., DDL, DML & DCL. Data Definition Language (DDL) deals with all the database schemas, and it defines how the data should reside in the database. Commands like CreateTABLE and ALTER TABLE are part of DDL.
Data Manipulative Language (DML) deals with operations and manipulations on the data. The commands in DML are Insert, Select, etc.
Data Control Languages (DCL) are related to the Grant and permissions. In short, the authorization to access any part of the database is defined by these.