More information is available at the community portal. You may ask questions at the help desk, village pump or on IRC channel #wikimedia-commons (webchat). You can also contact an administrator on their talk page. If you have a specific copyright question, ask at the copyright village pump.
The four tildes feature is provided for use when delivering messages on people's talk page (like the one I'm delivering to you now). It actas like a signature on the end of the message indicating the person who sent the message and the date/time (again, you will see it on the end of this very message). Obviously this information could be tracked using the page history, which records which logged on user made which edit, but it's much simpler to just use the signature method. Thanks Amakuru (talk) 15:15, 10 June 2011 (UTC)