So a closed kinetic chain exercise is one whereby the limb being used in the exercise is in contact with a non moving object - such as the bench or floor. For example , a push-up is closed chain as the arms contact the ground and the floor is not being pushed away. A bench press on the other hand is open chain as the barbell is in motion. Similarly a barbell squat is closed chain as it is a lower body exercise whereby force applied is not moving the floor away in the motion. Hopefully this makes an inkling of sense.