Suspension

Suspension is a weight transfer using the calves muscles so that the vibrations from the steps are not transferred into the body. The term is coined from a car’s suspension, which absorbs the shocks from the road.

The salsa basic should look like normal walking from everyday life, which uses all calves and the knee rarely bend excessively. The 2nd video is an example of the opposite, the lead here 'bounces' because he is bending at the knees.

To practice suspension, you must feel the foot 'rolling' from heel to toe and vice versa. This usually affects leads more than follows because follows are generally wearing heels and therefore their calves are almost always engaged anyways.