For Pros, it’s easy, but I hear a lot of people asking about the differences between impact drivers, impact wrenches, hammer drills, and drill drivers. It can really get confusing. Hopefully this will help to break it all down.
Impact wrenches are tools that have a square head to accept sockets. They are used for removing lug nuts or driving lag bolts. These tools vary widely is size and strength, so be sure to get one that will have the power you need to drive the bolts you have. Be sure to check the specs for torque on these tools, and make sure you get a high capacity battery as these application require a lot of juice.
Impact drivers are a more light duty tool. These tools have a 1/4″ hex quick connect on the end and accept standard insert tips for nut drivers or screw driving bits. They are great for running screws like installing drywall, metal studs, and home projects.
A hammer drill is a tools designed to drill through concrete. Most can also be used as a standard drill as well without the hammer function. This tool should typically only be ordered by someone needing to drill through concrete, but occasionally are used by pros who need the heavier duty capacity of the hammer drill without the hammer function.
Standard drill-drivers are the typical workhorse of cordless drills. The usually have a 3 jaw chuck that can accept any drill bit or driver bit with a shank diameter up to 1/2″. These are great for standard drilling through wood and metal and for basic screw driving applications. For someone looking for their first tool, this is where to start.