A tweetup is a real life gathering of more than one person that have come together through the online world of Twitter.
Basically what happens is a Twitter user organizes a tweetup by just choosing a location. This user then announces (tweets) the tweetup by updating his/her status on Twitter. People that follow this person are notified of the tweetup and often retweet the event to their followers.
If the person that organized it is popular enough this will result in a nice size gathering.
There aren’t really any rules to a tweetup other than you should assume you will be paying for your own food or drinks.
Sometimes companies will sponsor a tweetup and might ask you to follow them or to do something wacky like write the name of their company on your hand to enter. Tweetups can also be formed as a fundraiser for a certain cause. In this case, attendees can assume that they will be asked for a donation. Tweetups can also be formed as a sign of protest.
If you plan a tweetup expect that people will be tweeting from the event so it better be good otherwise the whole Twitterverse will know it sucked.
