just to add something that hasn't been said yet [i guess][i didn't even read all the posts]
des is also used if you don't know the exactly amount of something,like:
-> Tu as des pêches?
-> Il y a des livres
After saying the amount of the thing you're talking about you use de and then the thing without an article.for example:
->J'ai un kilo de farine.
see?the article la [la farine] will not be added
If the word/thing you're gonna use does begin with a,e,i,o,u, or h the la/le turns into l'
for example:
-> l'ecole
-> de l'eau
-> l'hôpital