DDL stands for Data Definition Language and is a subset of SQL that is used to create, modify, and delete database objects such as tables, views, and indexes. DDL commands are used to define the structure of the database schema and are used to create and modify the structure of database objects in the database. Some examples of DDL commands include CREATE, ALTER, and DROP. DDL is different from other SQL subsets such as DML (Data Manipulation Language) and DQL (Data Query Language), which are used to manipulate and query data within the database.