Cordless tools/machines are suited to a variety of different situations, as you are not limited to only working in places with power sources nearby.
A hammer drill contains a hammer clutch or a hammer-like mechanism which provides a circular rotation and a forward driving force. A hammer drill is capable of performing heavy-duty tasks, but it can also be used as a regular power drill.
A drill with a pistol grip handle is usually compact and lightweight, making the tool suitable for a large variety of applications and easy to use.
A keyless chuck drill enables you to change out drill bits rapidly without having to use any special keys.
A tool/machine with a higher voltage produces more power.
Higher speeds work better for drilling holes in certain types of material, such as steel, aluminium, concrete, etc. The drill speed is measured in rotations per minute (rpm) when the drill has no-load.