Ball-between-knees drill to stabilize the lower body
The coach demonstrates a lower-body drill using an object he sets in place: he bumps his hips while keeping the right knee on the inside so the left knee cannot touch (or 'kiss') the right, holding his anchor point and maintaining his brace. He frames it as an interesting way to use the lower body the right way during the swing.
Channel: PorzakGolf
Watch official source at 0:22Why this context matters
He uses an object held between the knees as a training aid.