Cordless impact drivers are one thing. Those store energy in a spring, a rotating hammer assembly is pushed by that spring and gains inertia, striking an anvil

Cordless impact drivers are one thing. Those store energy in a spring, a rotating hammer assembly is pushed by that spring and gains inertia, striking an anvil to provide a quick burst of torque. They typically have a hexagonal socket and are used to drive screws. Impact wrenches have the same construction, but are beefier, have square drive anvils, and are used to drive nuts and bolts. A hammer drill spins in a continuous motion, and is typically used with a spiral flute drill in a Jacobs chuck (or tool-less version of the Jacobs chuck). You can usually enable or disable the hammer action with the clutch. It has a similar mechanism that encourages the drill to tap forwards, but if you press too hard it won't do much. Just a weighty and useless add-on to an ordinary drill to justify a slightly increased price, IMO. A regular drill, even with a masonry bit, is ineffective in concrete; hammer drills can work if the bit is small and the mix used more sand and maybe fine gravel (eg. mortar or brick), but are hopeless if you encounter a larger stone. Importantly, the energy and the frequency of the hammering action are tied to the rotation - usually 1, 2, or 3 taps per revolution. You don't get heavy or rapid impacts at low RPM. A rotary impact (whether pneumatic, corded, or cordless) has an SDS head and a mechanism that drives the head forward and aft. You can typically run it in hammer-only mode, which is impossible with a hammer drill. You may be able to shift a cam (or adjust an air valve) to change the impact power. And yeah, with a decently powerful rotary impact tool, you can run put large holes in concrete with little hassle.