Plurals of the and a = les and des (articles)

Look at these examples:

 

The plural forms of le, la and l' is les

The plural forms of un and une is des

Note that when you say ''I have strawberries.'' in English, you are actually saying ''I have some strawberries.'', but in English, you can omit 'some'. 

NOT in French!

In French you must always use "des".
E.g. J'ai des fraises. 

See also Using du, de la, de l', des to express some or any (partitive articles)

 

Grammar jargon: Les is the plural definite article; Des is the plural indefinite article. These articles are used with countable nouns (things you can count, like dogs, as opposed to mass nouns for things like milk which use partitive articles instead.)