CUDA Compute Device says "(dislplay)" beside it. What does that mean? When I choose CUDA under Cycles Compute Device in user preferences, it gives me the option to use my GPU, but it also says "(Display)" beside it.

GeForce GTX 1080 Ti (Display)

Does this mean that my CPU will still be rendering my scene while my GPU just simply keeps the rest of my program updated visually? Or is this all in my head?

It seems to me like I'm going to need another GPU so that I can run both display AND rendering, which is very strange to me. Is this true? Because I really don't want to have to buy another one if I don't have to.
If your GPU is connected to a monitor (or multiple ones), then you'll see the (display) notice. That only means that the GPU is also being used to display images on a monitor.

Blender will still use it to render, just know that some of the resources of the GPU are going to be used to refresh the screen(s). If you have multiple GPUs you might see the difference.



In this example both GPUs are used for rendering, but one of them is using some resources to feed my monitors, while the other is used exclusively to render.