Let's understand more about DML , DDL and Actual Data.
DML is Data Manipulation Language which consists of update commands such as SELECT, INSERT, UPDATE , DELETE etc and ABAP Programs handle these commands.
DDL is Data Definition Language consists of commands such as CREATE TABLE, CREATE INDEX, DROP TABLE, ALTER TABLE, etc. and ABAP Dictionary handles the DDL part of SQL. It can be viewed as metadata.
Diving deep in ABAP Dictionary :-
1. Data Elements : Elementary type of definition the data type , length and possibly decimal places.
2. Structures : Components that can have any type.
3. Table Types describe the structure of an internal table.
The Dictionary supports the definition of user-defined types and these types are used in ABAP programs. They also define the structure of database objects such as tables, views and indexes. These objects are created automatically in the underlying database in their Dictionary definitions when the objects are activated. The Dictionary also provides editing tools like Search Help and locking tool like Lock Objects.
Data of the table / Actual Data : So what is store in that table is the actual data or data of table.
Those who have been following the migration series or understand migration , R3LDCTL takes care of ABAP Data Dictionary that is DDL part of SQL and RLOAD take care of the actual data that is stored in the tables. Just to add up in case of JAVA system, We only have JLOAD that manages both.