When do I have to use die, das, or der?

[EKP]

I thought I had to use them before a noun no matter what was in the rest of the sentence but it is now seeming more as though I use it when I literally mean THE _.

Example used in Duolingo:
Du isst Brot.

So, all in all, my question is actually- do I have to use them if I do not want to say 'the' before my noun?
I hope my question makes sense, thank you.

[McSupreme]

I think it's the nearly the same than in english. "Du isst Brot" -> "You eat bread", but "Du benutzt DEN Hammer" -> "You use THE hammer" .....

[Emily.Beuken]

It is the same in English. By saying You eat bread [Du isst Brot] you're making bread vague (vaguer than saying you eat the bread [Du isst das Brot]).