Understanding the science behind movements will help you understand how to do them most effectively and safely. Incorporating movement-stretching and mobility work such as Active Isolated Stretch and PNF Stretching help you in your functional range of motion.
Passive stretching helps with flexibility, which is helpful, but limited in its scope. Active mobility work develops your flexibility and strength in balance with each other, to increase your safe range of motion in movement.
Watch this intro before Practicing Active Isolated Stretch.