Varicella zoster is a virus that causes two distinct diseases: chickenpox and shingles. Chickenpox is typically a childhood illness characterized by an itchy rash, fever, and fatigue. It spreads easily through respiratory droplets or direct contact with the rash. After a person recovers from chickenpox, the virus remains dormant in the body and can reactivate later in life, leading to shingles. Shingles is marked by a painful rash, often appearing on one side of the body. Vaccines are available to help prevent both chickenpox and shingles, reducing the risk of infection and complications.