Trips are an OpenFlights feature for grouping together multiple flights across many airlines. Trips can be filtered and viewed separately in the statistics, and you can also share trips with others. You can even link your website, blog, FlyerTalk trip report etc. to your OpenFlights trip.
Example: You went on a trip all around Europe, and now you want to share a map that shows only your European flights with your friends.
Select New flight and switch to Detailed mode.
Enter the first flight and click on next to Trip to create your new trip.
Your new trip now appears in the Trip pull down. Add the flight.
Add your other flights. As long as your new trip is selected in the pull down, they will be added to the trip.
That's it! You can now choose your trip in the Filter, or click on to see the trip address for sharing with others.