TL;DR layman version, tessellation help flat object look more realistic by multiplying the amount of triangle/polygon.

For example, I disabled Tesselation in image below.

It look similar to the screenshot you posted(not the same but close enough, check the Canon head on the left side of the ship), and when i enabled wireframe view, this is the amount of polygons/triangles it need to render.


and when i enabled Tessellation, the image will look like this.

and when i enabled wireframe view...

the amount of triangles it need to render is HUGE compare to previous image with Tess off.



Manually set the Tessellation multiplier in CCC and rerun Heaven.

Don' run the benchmark in wireframe mode, it only make the score lower. Just take screenshot in this exact spot so we all can see tessellation level is correct.