"She eats bread."
Translation:Lei mangia il pane.
As someone who has learnt French before, I'm going to tell everyone that you're going to need to get used to the definitive article being used in a lot more places than it is in English.
Sadly, Duolingo seems to sometimes only accept translations in English with the "the" or without "the" exclusively--never both--making it confusing for learners.
"Il" and "lo" are both masculine articles. "Il" is used in most cases when the word begins with a consonant. However, if the word begins with s + a consonant, gn, pn, ps, x, y, or z, then you use "lo." And then "l'" is used for words that begin with vowels. Again, this is only for MASCULINE words. Feminine is easier in my opinion. "La" is used for most words, and then "l'" is used for words that begin with a vowel. Hope this helps :)
"Mangi" is 2nd person informal singular of the present (you eat) and 2nd person formal singular of the imperative, but I'd advise you to ignore that until the lesson on Formal You, because duolingo doesn't accept it in all instances. You can check the whole conjugation table on http://www.italian-verbs.com/italian-verbs/conjugation.php?verbo=mangiare; it uses the traditional pronouns (egli=lui, essi=they), so ignore them too.