Periodization involves systematically varying training specificity, intensity, and volume over periods or cycles to promote improvements in training and performance while preventing boredom. The goals are to optimize performance at key points, structure training to target physiological and performance outcomes, manage training stress to reduce overtraining, and promote long-term athlete development. Training is divided into macrocycles, mesocycles, and microcycles with different periodization models like linear, undulating, block, concurrent, and conjugate. Proper periodization requires understanding an athlete's schedule and needs to effectively plan preseason, in-season, and overall training.