The PlayStation 4 Pro's GPU has 36 compute units. These AMD Graphics Core Next (GCN) units run at 911 MHz and provide a theoretical peak of 4.2 teraflops.
The Pro, introduced in 2016, significantly upgraded the graphics hardware over the original PS4 and PS4 Slim. Those models use 18 compute units at 800 MHz, rated at 1.84 teraflops. The Pro therefore increased both the number of compute units and their clock speed.
Compute units are groups of shader-processing resources inside AMD GPUs. They help handle lighting, geometry, textures, and other visual calculations, but they are not the same thing as game levels, CPU cores, or total pixels. A higher compute-unit count generally offers more graphics capability, although performance also depends on clock speed, memory bandwidth, software optimization, and the game engine.
The Pro was designed to support enhanced visuals and 4K displays. However, many games used checkerboard rendering or other reconstruction techniques rather than rendering every frame at native 4K.