Unless you have used a hand drill, it's hard to imagine just how big a revolution power drills really were. Holes that represented a minute or more of work could be done in a matter of seconds. There's a reason why drills are so often the first power tools people buy. They aren't just an evolution over hand drills, they are a revolution.Drill Basics
The basic electric drill is based around a trigger-operated electric motor. Most have a switch near the trigger so you can choose forward or reverse operation, and they use a chuck to hold the bit in place while working. More powerful units plug into the mains, but as battery technology improves, more and more drills are ditching the cord for increased mobility and flexibility.Cordless Drills
Cordless drills rely on a battery in the handle for power. Early models used nickel-cadmium batteries, while later designs shifted to lithium-ion batteries. Whenever possible, look for a lithium-ion drill as it not only provides more power, but also operates at full power throughout its operating range. A 10.8 Volt cordless drill is good for light work, but if you want to take on bigger projects, you should probably consider an 18 Volt unit.Hammer Drills
The advantage of a hammer power drill is that it adds percussive force to rotary motion, making it much more effective when working with masonry. Most use a dual-disk system with a set of ridges that add a linear component to rotary motion as the disks rise and fall across the ridges. They require more effort on your part, but are very effective.Using Drills
The most important piece of advice for using a power drill, especially a cordless one, is to let the drill do the work. When you lean into most drills, the pressure makes it harder for the bit to turn, so you're adding to the load on the motor. Letting the drill work both saves battery power and keeps the motor from overheating.