You should see a video screen front and center that is playing some sort of video or visual animation, and if you have your speakers turned on you should be hearing some audio from the video. Below the video are avatars representing all of the other people that are in the community with you at that very moment. At the bottom is one avatar facing the opposite direction, dancing behind the DJ booth -- that is the current DJ and they are playing the video you are seeing. In front of the DJ is your avatar in the front row.
Any avatars that are dancing are doing so because they like the video that is currently playing.
To the right side of the screen is the live chat where you can communicate with all of the other community members.