There are three tools that look very similar at Home Depot and may seem largely interchangeable, but have slightly different usability and functionality: the power drill, the impact driver, and the hammer drill.
The power drill has the longer snout and locks in screw bits and drill bits with a chuck. This allows for versatility for quick projects around the house that don’t require a lot of drilling. Power drills often have adjustable speeds and torques depending on the material you are drilling – softwoods, hardwoods, metals or stone. Because of the chuck, a power drill can hold just about any type of bit – cylindrical, hexagonal and their various diameters. A power drill is probably where you want to start off when building your collection of home tools.
Now, if you start tackling larger projects – putting in decking, building a shed – projects where the hole placement is not extremely important, but you have a lot more fasteners to get through, you may want to think of adding the impact driver to your collection.
While it is totally doable to use the drill for this purpose, the impact driver is built in such a way that it has very high torque, and rotates the bit in small repetitive intervals, giving it the name impact driver. This prevents slippage and drives screws into even knotty wood very easily. Impact drivers also do not have chucks, but instead quick release hex mating collets. It drives screws in quickly and efficiently with less slippage and with less applied force, which is easier on the wrist and prevents stripping the grooves on the screw head. The one drawback is that it tends to be a bit inaccurate compared to using a drill, but at such a large volume of fasteners, and placement does not have to be very precise, the impact driver makes short work of large projects.
The third piece of equipment that seems like a hybrid between a power drill and impact driver is a hammer drill. A hammer drill is actually very similar to the regular power drill, but has induced vibrations that cause hammer-like impacts to force fasteners and drills in a bit harder. Hammer drills are more commonly used for drilling into concrete, brick, stone, and other masonry. Newer hammer drills can function like regular power drills with a built-in feature to disable the hammer vibrations.