The difference between definite and indefinite articles is actually important in French as many mistakes are made by confusing them as sometimes in English no article is used ...
J'aime les chats tigrés = I like tabby cats
You use the definite article 'les' as it is presumed you like all the cats who come under that specification.
J'ai des chats très exigeants à la maison! = I have (some) very demanding cats at home!
In this example you don't know which cats you are referring to , how many there are or what type of cats , so you use the indefinite article 'des'.
For more details take a look at the following lessons on each set of articles:
Hope this helps!