Quality-adjusted life years (QALYs) are a measure used to evaluate the value of medical interventions. They combine 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 make informed decisions about resource allocation. By comparing the QALYs gained from different treatments, they can assess which options provide the best health benefits relative to their costs, ultimately aiming to improve overall patient outcomes and efficiency in healthcare systems.