A Quality Adjusted Life Year (QALY) is a measure used to evaluate the value of medical interventions. It combines both the quantity and quality of life gained from a treatment. One QALY equates to one year of life in perfect health, while less than perfect health is represented as a fraction of a year. QALYs help healthcare providers and policymakers assess the cost-effectiveness of different treatments and allocate resources efficiently. By comparing QALYs across various interventions, they can make informed decisions about which therapies offer the best overall benefit to patients, considering both longevity and quality of life.