Raised beds are a popular forming of gardening - especially for vegetables and other food annuals. A raised bed is a raised area typically between 6in and waist height above the surrounding soil. Various materials are used to keep the bed in place, although timber is probably the most popular. The soil usually contains a large proportion of compost - especially as a bed has to be filled with external material (this makes it easy to mix large amounts of compost in with little additional effort).
Raised beds are an excellent solution to poor top soil, they also avoid compaction due to walking on the soil. If planted correctly, they can also reduce weeds and help control moisture loss (although excessive drainage may require more watering) if designed properly. The raised nature of the beds can also make them ideal if bending over is a problem: Waist-high beds are particularly popular with the elderly.
Raised bed gardening is often combined with the square foot gardening and companion planting concepts.
Use this tag for all questions specific to raised bedding: Eg. how to build a raised bed, how to water, etc.