Fitness levels refer to an individual's overall physical condition, which can be assessed through various factors such as strength, endurance, flexibility, and body composition. These levels can vary widely among individuals based on their age, genetics, lifestyle, and exercise habits. Measuring fitness levels often involves tests like the Cooper Test for cardiovascular endurance or the Sit and Reach Test for flexibility. Understanding one's fitness level can help in setting realistic health goals and creating effective workout plans tailored to improve specific areas of fitness.