Proper GPUs

The Installation chapter says, " Before installing any deep learning framework, please first check whether or not you have proper GPUs on your machine (the GPUs that power the display on a standard laptop are not relevant for our purposes). For example, if your computer has NVIDIA GPUs and has installed CUDA, then you are all set."
So it begs the question how do I check whether I have proper GPUs or not? And what is proper or improper?
And then, is CUDA mandatory?
For example, my (old) computer has an Nvidia card with GPUs but I have been unable to install CUDA. But I can install tensorflow.