Gmail has launched a new feature called "Quick Actions," which recognise certain types of messages and help you take action on items immediately.
For example, if your friend sends you a Google Calendar invitation, you can RSVP right from your inbox by clicking the RSVP button. It will also recognise if you ate at a restaurant and ask you to rate it or — even cooler — show you all your flight information at the top of the message if it detects a confirmation email.
Check out the full post at Google's blog for more info. You should see these buttons roll out over the next few weeks, with more actions to come.
Take Action Right From the Inbox [Official Gmail Blog]