"The cat eats bread."
Translation:El gato come pan.
Because they are not referring to any particular bread, just bread in general. But if you mean a particular bread you have to use "El" in front of it, because "Pan" (Bread) is a masculine word in spanish, which should always have "El" in front. The main rule is: "La" in front of feminine words and "a-ending" if you are refering to a feminine word or a female and "El" in front of a masculine word that also should have an O-ending, and also if you are fering to a boy/male. Pan is a special word because it does not have the main "masculine O-ending", but it´s still a masculine word and should therefore have "El" in front of it.
This is actually one of the major drawbacks I'm finding using duolingo. Some of the time it feels like they've just mashed the parts of speech together to make sentences that may be grammatical, but are borderline nonsensical.
When, in day-to-day speech am I going to tell someone that my cat eats bread. Cats don't eat bread.