Chickenpox (varicella) is a highly contagious infectious disease caused by the varicella-zoster virus. It is characterized by red, fluid-filled, and itchy lesions appearing on various parts of the body. Primarily seen in childhood, chickenpox manifests after an incubation period of 11 to 21 days with typical skin rashes, fever, headache, and sore throat. While often considered mild, causing discomfort and irritability in children due to the intense itching of the rash, chickenpox can lead to serious complications in immunocompromised individuals or those with specific immune deficiencies.