Chickenpox, also known as varicella, is a highly contagious viral infection caused by the varicella-zoster virus. It primarily affects children but can occur in individuals of any age. The disease is characterized by an itchy, blister-like rash that usually starts on the face, chest, and back before spreading to other parts of the body. Chickenpox is generally mild in children, but it can lead to more severe complications in adults, pregnant women, and individuals with weakened immune systems. Vaccination is the most effective way to prevent chickenpox and its associated complications.