They’re riding what’s called an artistic bicycle. It’s a special bike with special geometry and proportions to allow the riders to do acrobatic moves on the bike. Artistic bicycling is a competitive sport in parts of Asia and parts of Europe.
There’s information about it here: UCI Indoor Cycling
The site mentions both artistic cycling and a sport called cycle ball. The bikes for each are different but also similar. They’re fixed gear so they can pedal forwards and backwards.
You can Google and find videos of both artistic bicycling routines and cycle ball.
I last went to the (indoor cycling) world championships in 1986. That year it was in “Genk” Belgium. I represented the United States along with Unicon II host Greg Milstein. We didn’t do so hot, but we weren’t last place either…
Our sport of Standard Skill comes directly from that sport. Sitting on the tiny head tube of a fixed-gear bicycle, even without a guy standing on your shoulders, is painful and difficult. Note the relative “seat height.” And odds are, the guys in the picture are going backward.
It’s an amazing sport, but the lack of any creativity whatsoever, other than choosing the order of your routine, is probably what keeps it from going worldwide.