Chickenpox is a highly contagious viral infection caused by the varicella-zoster virus. It is characterized by an itchy rash that develops into fluid-filled blisters, along with symptoms like fever and fatigue. The infection is most common in children but can affect individuals of any age. The virus spreads through respiratory droplets or direct contact with the blisters. Vaccination is available and is the best way to prevent chickenpox. Most people recover fully, but complications can occur, especially in infants, pregnant women, and those with weakened immune systems.