In french, when do i use de la or un or l'?

Question:

In french, when do i use de la or un or l'?

Best Answer - Chosen by Asker: de la applies to feminine
de le to masculine
de l' before a vovel sounds better
de la Lune==from the Moon
de le Soleil=from the Sun
de l'ocean=from the Ocean
Sorry, my grammar is a bit rusty.