A sander is a very useful power tool but for most people an electric drill is more useful than a sander. The drill is the first power tool most people buy. Although the drill is a simple tool, you have a number of different models to choose from. Here is a short drill introduction, explaining the basics.
The drill is a very old tool, very simple drills, a pointed stone spun between the hands, have been used for thousands of years. The first bow drills appeared more than 6000 years ago. Most drills have been manual but simple drill presses powered by water wheels or wind mills have been around for centuries. The first electrical drills appeared towards the end of the 19th century.
Hand drills are still useful today, if you are into woodworking a hand drill is useful for a lot of small drill jobs. But in most cases, an electric drill is much better investment for tasks around the house. Nowadays, a cordless drill can be the best choice for many. Thanks to improved batteries, cordless drills can be used for heavy drilling as well. Note that most cordless drills can also be used as screwdrivers. The drill needs to have a reversible engine and support low speeds.
Pneumatic drills are popular amongst some professionals but for tasks around the house, they are far too expensive. An electric drill is much cheaper and easier to use.
The main advantage of a cordless drill is that you are not limited by the cord. But a corded drill has also couple of advantages. First, corded drills are generally cheaper while not performing worse than cordless drills. With a cordless drill, the battery may go flat before the job is finished. Obviously, this is not an issue with mains-powered drills. A corded drill is often a better choice if you do a lot of heavy drilling. But by having two quick-charge lithium-ion batteries, you can work non-stop with a cordless drill, except for the few seconds it takes to change the batteries.
If you are going to drill in hard materials, such as concrete, you need a hammer drill. It adds a hammering action that makes it easier to drill in hard materials. Using the hammering action in soft materials is not recommended, you will end up with a much larger hole than planned and probably damage the material as well. Hammer drills have a switch allowing you to disable the hammering action. This turns the hammer drill into a normal electric drill. Thus, the hammer drill is a versatile drill, it can be used for drilling in most materials. Some hammer drills can also be used as screw drivers.
Note that the hammering drill requires a lot of energy. A corded hammer drill is often a better choice than a cordless model if you are going to use the hammering action a lot. The battery in a cordless drill is quickly drained by the hammering action.
Of course, a good drill is only part of the story. You also need good drill bits. You can even turn a drill into a sander with the right attachment.