The Genome Health Assessment is a technology that looks at the current status of the human Genome (which has a total length of about 3 billion base pairs: Source- Wikipedia) to get an accurate idea as to whether a person is ageing at a healthy and balanced rate, and if not, how it can be cured timely.
Also, GHA looks at a certain network of genes to detect your risk of diseases like high blood pressure, heart ailments, cancer etc. It can study all these genes together, ascertain your risk factor and determine how rapidly your DNA can recover from those diseases. By measuring telomeres in Genome, cancer can be detected and treated early. If scientists become able to block telomerase activity in cancerous cells, they can stop the growth of these cells altogether.