DDL-Data definition language

A data definition language or data description language (DDL) is a syntax similar to a computer programming language for defining data structures, especially database schemas.

In Djanog, what the DDL is the Migration operations. You just change the model in Djano and it will create migration operations automatically for you and run sql like this migrations.RunSQL("INSERT INTO musician (name) VALUES ('Reinhardt');")

References:
https://en.wikipedia.org/wiki/Data_definition_language
https://docs.djangoproject.com/en/1.11/ref/migration-operations/