Water distillation is one of several methods of water purification. In distillation, water is boiled to produce steam. As the steam separates from the water, it leaves behind solids and dissolved gasses. This steam is then condensed into purified water and collected in a tank and stored for use as needed.
The advantages of distilled water over water produced by other water purification methods are that it will not cale-up water-using appliances (like your coffee maker, iron, or clothes steamer), and the water does not contain any undesirable contaminates (like dissolved solids or chlorine). Unfortunately, many individuals do not like the taste of distilled water as much as regular tap water, because distillation removes the dissolved gasses that give water its pleasant taste -- distilled water tastes flat. However, distilled water is excellent for cooking where the lack of minerals can actually enhance the flavor of the food.
Distillation is an option where the ground water contains an objectionable odor, a bad taste, or undesirably high concentrations of dissolved minerals. Distilled water can either be purchased in stores or generated in a home using a commercial distillation unit. Some models are portable and require no plumbing. Just plug them in and fill with tap water. Other models are available that conveniently fit under most sinks or counters and produce up to four gallons per day.
Larger non-portable units are capable of producing 8-12 gallons per day. An advantage of distillation over some other methods of water purification is that it does not require changing filters. A disadvantage is that it can use a significant amount of energy to operate.