It can be used, only with IMPDP. This helps in generating the DDLs from a dumpfile.
Suppose I have dump file of table DBACLASS.DEP_TAB . If you need the DDL of the table, then use SQLFILE with IMPDP command as below.

This will not do the actual import. It will just dump the metadata (DDL) of the table in the specified .sql file.

parfile will look as below:

Now check the sqlfile(emp_tab.sql):

This method can be used to get DDL of any type of object(INDEX, TABLE, PROCEDURE, PACKAGE ETC) from the dump , without actually doing the import in the database.