DML = Data Manipulation Language - these are the queries you use every day to manipulate data
DDL = Data Definition Language - these are the queries you would use to create/delete/or change tables. They are not normally used in applications because you would not normally be creating or modifying tables on the fly.
DSL? There is a third SQL language and it manipulates security objects.
Two cases I use DDL in applications which have SQL Server BE's:
1. If you use views that don't have indexes, when you link them initially Access asks you to define the unique index. The problem is that when you relink the tables or swap a BE from test to prod, you loose the index and the view is no longer updateable. The easy solution is to run a DDL query to add a pseudo index to the View. This query when run from Access does not alter the BE database. It just creates a pseudo index so Access knows what the unique index should be.
ALTER TABLE dbo_LU_TRM_RSN_IBC126_VW ADD CONSTRAINT NaturalKey UNIQUE(PCR_CD_NO);
2. If you use pass through queries, you need to refresh their connection strings when you swap BE's. I use DDL for that also.
Any DAO command you can write and run with VBA ca be coded as a DDL query and run that way.