This document discusses health-related and skill-related fitness. It defines physical fitness as the ability of the body to work efficiently and do work with little effort. Health-related fitness includes cardiovascular endurance, strength, muscular endurance, flexibility, and body composition. Skill-related fitness includes agility, balance, coordination, power, reaction time, and speed. The document emphasizes that cardiovascular endurance is the most important component for health and describes how to develop it using the FITT principle of frequency, intensity, time, and type of exercise.