Nos is the plural possessive article for nous. Nos besoins. Nos fruits. Nos enfants. Notre is the singular possessive article for nous. Notre enfant. Notre maison. Notre journal. Nôtre is used with le or la to mean "our one/ours". I don't know the grammatical term. "C'est la maison de qui ?" "C'est la nôtre". "Il est bon, ce gâteau" "Merci, c'est le nôtre". *I'm not native so grammatically the structure of those last 2 examples might not be 100% but the explanation is good.