The document discusses Data Definition Language (DDL) commands in Oracle such as CREATE, ALTER, and DROP used to define and manipulate database objects. It provides examples of using these commands to create tables with various constraints, alter table structures, create views, sequences, and indexes. The CREATE command is used to define tables, views, indexes and sequences. ALTER modifies existing objects and DROP removes them permanently. Constraints enforce data rules. Views display data from other objects. Sequences generate numbers. Indexes improve data retrieval performance.