It sort of explores the idea of happiness all throughout the world, not only talking about how to be happy, but also following the lives of certain people who are very happy today, despite horrific events that have occurred in their past. It also shows different cultures in the world who are the most happy or the most unhappy, and includes several interviews with psychologists who discuss the ways to measure happiness.
It is very interesting and incredibly touching! I highly, highly recommend it. You can find it on Netflix available for instant streaming. Here is the trailer!