Not really sure whether this is the answer you are looking for but they all mean the same thing "of the [noun]" or "some [noun]"

Use "de la" when the noun is feminine.

Use "du" when the noun is masculine. "Du" is simply the contraction of "de le".

Use "de l' " when the noun begins with a vowel or a mute 'h', regardless of the noun's gender.

Hope this helps,