This document defines and discusses various aspects of physical fitness. It describes motor-skill fitness and divides physical fitness into three types: agility, balance, coordination, power, reaction time, speed, cardiovascular fitness, flexibility, muscular endurance, muscular strength, and body leanness. It outlines the benefits of regular exercise, including improved strength, coordination, flexibility, energy, and cardiovascular health as well as prevention of diseases. Exercise is also believed to reduce stress and tension, improve sleep, attitude, and self-confidence. The document concludes by discussing the need for well-planned exercises and outlining three principles of exercise: overload, specificity, and progressive principles.