Also called herpes zoster, this is caused by the same virus that causes chickenpox. If someone had chickenpox, the virus stays in their system for life. Anyone who's had chickenpox can get shingles later (but this usually won't happen until someone is an older adult).
Shingles causes a rash with blisters on the body that can be very painful. The blisters are contagious and can spread the chickenpox virus to people who never got chickenpox and didn't get the chickenpox vaccine.