In Cut-out animation, keyframes are used to record your poses in the Timeline view. As you manipulate your digital puppet, you will create keyframes in the Timeline view which record the new coordinates of the elements being manipulated in your rig. In Harmony you have the option to create individual keyframes for your key poses, breakdowns and in-betweens or to allow the software to interpolate between your set keyframes.
NOTE Key poses are keyframes used to block poses, somewhat similar to what you would see in Traditional Animation.