Varicella zoster virus causes both chickenpox and shingles. It is one of eight herpesviruses that infect humans. Chickenpox results from initial exposure to the virus and presents as a mild childhood illness characterized by a rash. The virus can remain dormant in nerves after chickenpox and reactivate later in life to cause shingles, a painful dermatomal rash. Complications are more common in adults, immunocompromised individuals, and neonates exposed maternally. Treatment focuses on antiviral medication for severe or complicated cases. Vaccination provides effective prevention against chickenpox.