THE PARTITIVE DE AND THE CONTRACTION OF DE + LE

Du is a contraction of de+le—"of the, from the." When de precedes the definite article le, it is contracted to du. There is no change with la or l'.

Il est à côté du café.
It is next to the café.
Nous sommes en face de la rue.
We are facing the street.

To express the notion of "some," the French often use a form of de plus article.

Isabelle va prendre de la limonade.
Isabelle will have some lemonade.
Je voudrais du café.
I'd like some coffee.

Whenever one can count the items individually, "some" is expressed by des; when the items fall under the category of non-count nouns, the French, however, use de plus an article.

Je voudrais des pains de campagne.
I would like some country breads. 
Je voudrais du pain.
I would like some bread.

In front of masculine and feminine singular nouns starting with a vowel or silent h- use de+l'

Je prends de l’eau.
I take some water.