Google+ Events were announced and launched at Google I/O on June 27, 2012.
As you'd expect it allows you to create an event and invite people, even if they're not Google+ users.
Among some of its neat features:
- Themes, featuring cinegraphs (animated GIFs with subtle movement to them) to personalize the event
- Integration with Google Calendar (automatically adds to your calendar; allows you to check your availability). Google+ Events in your calendar are distinguished from your usual calendar entries with the profile photo of the Google+ Event organizer
- Integration with Hangouts, in that you can create "Hangout-only" events. (I even think it launches the Hangout app for you)
- Party Mode: If you use the Google+ app on your mobile device during the times of the event, you'll be asked to automatically upload your photos taken during that time to a shared album for the event. They get added in real-time; during and after the event everyone's pictures will be displayed in chronological order.
More information at the official announcement.