What's the difference between data definition language and data description language? Are they the same thing? Which one does DDL stand for? Here's what my understanding is, but could potentially be incorrect:

Data definition language:
Contains names and types and field length etc. of the attributes in a table 

A database about a database - stores metadata 

DBMS refer to these during the running and maintenance of a db

Data description language:

Function used by RDBMS to craete a database from nothing 

Defines a database's table using Validation rules, field types, auto-incrementing requirements, primary kets etc. 

Results in a final table design, aka  a schema

It's likely that I've gotten it all messed up, would appreciate some wisdom on it. Thanks.
DDL (Data Definition Language): Used for defining data structures and schema like CREATE and ALTER commands.

DML (Data Manipulation Language): Used for managing data with schema objects like SELECT commands.

DCL (Data Control Language): Used to control data like REVOKE and GRANT commands.

TCL (Transaction Control Language): Used to manage the changes made by DML statements like COMMIT.

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