The yellow dots are aircraft.
It is a 24 hour observation of all of the large aircraft flights in the world, condensed down to about 2 minutes. You can tell it was summer time in the north by the sun's footprint over the planet. You could see that it didn't quite set in the extreme north and it didn't quite rise in the extreme south.
Notice that as evening approaches, the traffic is predominantly from the US to Europe and when daylight comes, the traffic switches and it is predominantly from Europe to the US.
From Bill Granger