DML and DDL Commands in SQL are two main types of SQL commands. DML commands are used to manage and manipulate data within existing database objects. Common DML commands include `INSERT` (to add data), `UPDATE` (to modify data), and `DELETE` (to remove data). On the other hand, DDL commands are used to define and manage database structures and schema. Examples of DDL commands are `CREATE` (to create tables, databases, or other structures), `ALTER` (to modify existing structures), and `DROP` (to delete structures). Both DML and DDL are essential for database management and operations.