That's a planche, which is a leverage/extension movement.. In the picture it's a ab planche. Gymnast include planches in their usually training protocol. Very difficult to master and very many different forms or versions.
Some version's are done from poles, exercises ladders, overhead bars, dipping bars, etc. The one's where someone holds their body straight out to a 90 degree angle are called flags. Sure there must be other names like dragon flags, as suggested. Martial artist use planche's in serious training...so maybe the dragon flag title came from that (guessing here).
Easier for lighter weight, smaller guys to master the planche, than for taller, heavier people like myself (I've never done one in my life). In any case, a superior ab and lower back movement well worth the effort. Don't like to use this overdone phase but the planche is an exceptional "core exercise" exercise.
Could easily adapt this movement into any BB'ing, crossfitness or lifting training plan. But first learn how to do it correctly, like any other exercise.
Good luck.
Side bar: photo from a Rocky movie, with Sly on the bench..no doubt.