MASCULINE AND FEMININE - "a" and "some"
ARTICLES 01 explained about masculine and feminine nouns, and ARTICLES 02 gave you the definite article for plurals - so you know how to say "the" for masculine [le] and feminine [la] and the plural of both of these [les] / [les].
Suppose, though, you want to say "a" instead of "the"? As in "a book", or "a table". You need to use "un" (which also means "one"); or the feminine form, "une". This would give you "un livre" and "une table".
The nearest thing you get to a plural of "a" in English, is "some". In French this translates as "des" - so you get "des livres" and "des tables" for "some books" and "some tables".
In English, though, you can have "some" of a singular item, as in "some cheese", "some salad" and "some water". These translate as "du fromage (m), "de la salade" (f) and "de l'eau" (f).
Why? Because, in French, these "articles" are made by adding "de" in front of the definite article (which as you'll recall, was le, la, l' or les). Sometimes putting these words together gives a shortened form, as in "du" and "des". You need to learn these!
| de + le = du |
de + la = de la |
de + l' = de l' |
de + les = des |