The first principle is that nouns are rarely left alone in French. In particular, articles are used where the English skip them.
"She eats bread" = she eats some bread = a certain quantity of bread
In French, that notion is expressed with construction : de + definite article - with the masculine definite article "le", de-le is contracted in "du" -> elle mange du pain - with the feminine definite article "la", no change: "de la" -> elle mange de la soupe
But 'She eats bread' isn't always about a certain quantity of bread. It could very well be a question of eating bread in general, right? Whereas 'Are you eating bread?' would be more time specific and thus about a certain quantity.
I ask this because I had some troubles with it in an earlier question.
Someone in another thread left a comment about this that I've found helpful in combination with Sitesurf's explanation: where the noun is the object of an active verb, the article is indefinite, e.g. "elle mange du pain," and where the noun is the object of a verb of appreciation (like, love, hate), the article is definite, e.g., "elle aime le pain."
Why is 'mange' translated as 'eats' as opposed to 'eating'? I'm assuming that 'mange' isn't translated as ate because the sentence is present tense. So, in this sense, it seems to make more sense -grammatically- to suggest that 'she is eating some bread', right? I guess I'm confused by the language used.
In English, to mean that an action is in progress at the time you speak, you use the continuous verbal form, ie verb BE + action verb in the gerund form (-ing).
o she is eating means she currently eats
In French, this verbal form does not exist (directly translated “elle est mangeant” is incorrect).
Therefore, you can translate either “elle mange” or “elle est en train de manger”, where the construction verb être + en train de + infinitive correctly expresses the English continuous form.
If it were pomme it would have been de la pomme, not du pomme, I think.