Those columns basically you can do operations on them right so i could say create like a query of book let's say order by you know book name dot deaths or just ending. also ties into when you're talking about doing the queries those columns play multiple roles letting you do the queries as well as defining the schema and the constraints  rightYeah so funny funny story also is that it wasn't like that in the beginning it used to be that you'd you'd have your mapper and your class but the class itself wouldn't have these attributes directly on it It used to be you had to act still talk to the table of this if you had an instance of my class dot foo versus an