Quite simply, it's a place for your group. If you have a group and need a way to manage events and members, this is your place.
Groups Place was started as a result of unhappiness at a popular site where people got together to meet up. Organizers found that they kept losing control of some of the features that helped them organize their group and needed a place where they were more in control.
Groups Place a site for established groups, or new groups that have ways to attract new members.
Although we'd like to say "if you build it they will come", this isn't a big enough site yet to have a global membership that would funnel members to you. If you'd like to start a group here and don't already have members, there are a few things you can do: