Your photo shows a track end, so that suggests your bike has not got a derailleur for gears.
Therefore it is a single speed bike. I cannot see an internally geared hub.
Trackends suggest it could be a track bike, but the wheel rim is in shot and it looks like a 20 inch wheel. Therefore you probably have a BMX.
The rear wheel mount plates are welded to a single-piece curved tube that forms both the chainstay and the seat stay. This looks similar to a Pirhana or Fuji from the `70s - see This Question for a similar shape.
From Can you identify this bike/frame?