There are many different types of drills out there on the market that are each used for different applications. We would like to help you by explaining each type and its uses.
Engineering Drills are used for either high torque or high RPM applications. Specially designed drills are also used in medicine, space missions and other applications. Drills with pistol grips are the most common type in use today, and are available in a huge variety of subtypes. The larger & slower the drill, the bigger the job. eg. for drilling 3mm holes in Aluminuim you'd want high RPM. For drilling 15mm holes in telegraph poles you'd want a larger, Hi Torque drill.
Impact & Hammer Drills are the most common domestic use drill type. They do all kinds of things besides simply drilling holes. Impact Drills can drive screws into any number of materials. Supplemental pressure, operated by a manual feed, describes how impact drills work in to aid in boring faster into concrete, rock or other challenging materials. Hammer drills can either be a drill or a replacement chuck that is installed on a impact/power drill. When the drill is set to "hammer drill" position it allows the chuck to move backward and forward over a short distance, allowing a spring to be compressed.
Rotary Hammers are similar in that they also pound the drill bit in and out while it is spinning. However they use a piston mechanism instead of a special clutch. This causes them to deliver a much more powerful hammer blow. Rotary Hammers require special bits which can lock into the Rotary Hammer and continue on spinning while smashing away.
Angle Drills are a power drill that features a chuck that is orientated at a 90-degree angle compared to the rest of the tool. A chuck is the clamp that holds the bit or other tool on the drill. This type of drill is most commonly used by plumbers and electricians because of its ability to work in tight wall spaces.
Mixer & Stirrer Drills can be used to mix various materials. Some materials you will need a more powerful drill than others. Paint for example will need less power than plaster so it is important you have the right drill for the job or you will be at risk of burning out the electric motor.
Core Drills are drills specifically designed to remove a cylinder of material, much like a hole saw. Core Drills are used for many applications, either where the core needs to be preserved or where drilling can be done more rapidly since much less material needs to be removed than with a standard bit.