This is similar to normal drill machine as mentioned above, but it has an additional gear mechanism as shown below
When you turn the rotary switch to impact drill mode it will engage a pulsating gear to the drill spindle and make the drill bit to move forward and backward towards the wall, which works like a chisel while it rotates to break the stone and hardened cement.
Impact drills are used for multiple applications like drilling on brick/masonry wall, concrete(without reinforcement) when you put the machine on impact mode. you can use it as a normal drill for drilling on wood, metals, plastics and screw driving when you put it in normal drill mode.
3.Rotary Hammer/Hammer drill/SDS hammer/Combi hammer etc: