Apparently rabbits believe in good manners, and part of that is always acknowledging you when they are passing you by. They expect no less from their fellow bunnies and apparently even their humans! My bunnies never pass by me without nudging me, and ive learnt to always give them little pet on the head (human nudge) whenever i pass them too.
When Pippin wants attention he will nudge me several times and then groom me, or if i put my hand down towards him he'll put his head down so i can "groom" him. When he is just acknowledging i am there he will give me a nudge and then continue on his way. If he keeps nudging me without any licks and stands there and stares at me, then i know he wants me to move, and if he starts digging at me then that's usually a sure sign.
A nudge can mean so many different things, it takes time to learn what your rabbits are trying to tell you, and they might not all communicate the same things to you in the exact same way. It wont take long for you to understand what he's trying to tell you, though im sure everyone still gets it wrong from time to time.
WTB Universal Translator.
EDIT: Oops, and by he i meant she. >.<