If you do Parkour you will need to learn how to land properly. As you gain more experience, you will try to climb and jump off higher and farther objects, and proper landings will become the most important techniques to have mastered.
Learning proper form for a basic landing is essential for beginners and experienced traceurs alike. You will use basic landing technique in almost every movement you do. But, it is particularly important to understand these principles when landing from heights. You can get away with poor landing technique from a short distance, but not from a high one. Bad technique from a high distance can leave you with nagging aches and pains.