Open kinetic chain exercises of the lower limb are movements, where the distal segment is unloaded and free to move. The opposite is true of closed kinetic chain exercises, whereby there is enough resistance to prohibit free motion.
Closed kinetic chain exercises are movements such as squats, Pendulum Squat Pro, leg presses and lunges, while open chain exercises are actions like leg curls, leg extensions and the Pendulum Reverse Glute Ham.
The kinetic chain can be understood as interrelated joints and body parts working with one another during motion. This creates a chain of events that affects the movement of neighboring joints and segments.
The advantage of open chain movements is that they tend to be better at isolating muscle and often are selected for specific rehabilitation and used to accentuate performance. While closed chain movements in general would be classified as more functional and closely approximating movements that are used in sport and daily life.

Open Chain Reverse Glute Ham

Closed Chain Pendulum Power Squat Pro

Closed Chain Pendulum Power Squat Pro XT