Shingles is part of the herpesviridae virus family (which is also responsible for oral and genital herpes). Once infection sets in, all herpes virus work the same: they hide in the nervous system, where they lay dormant for weeks or months (in the case of oral and genital herpes) or years (in the case of shingles). The herpes zoster virus is responsible for both chickenpox and shingles. After catching varicella zoster virus (chickenpox), the virus mutates into the herpes zoster and hides away in the nerves of the spinal column or at the base of the skull. From this point on, the shingles virus is dormant and living inside of the body. There is no cure for shingles, so the virus will remain latent in the body for the rest of your life.
Shingles itself is non-contagious, though this comes with a caveat. You cannot give another person shingles, but if someone else touches your wound, and they have not had chickenpox, they will contract chickenpox from your shingles. Later in life, the person might get shingles themselves.
Shingles generally occurs in people who are over 50 years old, with a higher chance of symptoms as the person gets older. The first signs of shingles becoming active can seem very minor; headache and flu-symptoms without a raised internal body temperature are common indicators that you may be getting shingles. An itchy or tingling area on the body found in a small patch or strip will be an indication of where the shingles will appear within a matter of days or weeks. When the virus becomes completely active, the symptoms can be quite severe. The rash that appears will be covered in painful, fluid-filled blisters that will be more painful than they are itchy. After about five days to a week, the blisters will burst and scab over. After about two to four weeks, the rash will be gone though scars may remains. Sometimes a condition called posteherpetic neuralgia can occur and be chronically painful for months or years, though this happens in less than 1% of cases.
It is possible that the virus will never become activated, and you will have no symptoms from the virus if this is the case. Regardless, there is a vaccine and there are medications that can help reduce your chances of getting shingles in the first place.