The floor caps your range and saves your shoulders while it loads the chest.
Let the elbows touch down and pause, do not bounce off the floor to start the press.
Pressing from the floor cuts the range short right where the shoulders would normally hit their deepest stretch, so the chest and triceps handle the top half of the press where they are strongest. The pause with upper arms resting on the floor kills the stretch reflex, forcing a dead-start push on every rep. It builds lockout strength and pressing volume for lifters whose shoulders complain about full-range benching.
The floor stops your upper arms before the deep stretch a bench allows, shortening the range and shifting emphasis toward the triceps and the lockout. Bench builds the full movement, the floor press builds the top half and gives cranky shoulders a break.
Either works. Bent knees with feet flat is the common setup and feels most stable, straight legs remove any temptation to use leg drive. Pick one and keep it consistent so your numbers mean something.
A brief, genuine settle, roughly a beat where the upper arms rest and the tension resets. Bouncing your elbows off the floor is both pointless and a good way to make the exercise hurt, so treat every rep as a dead start.
