Bonsai is a Japanese art form using miniature trees grown in containers. Similar practices exist in other cultures. The Japanese tradition dates back over a thousand years, and has its own aesthetics and terminology.
The purposes of bonsai are primarily contemplation (for the viewer) and the pleasant exercise of effort and ingenuity (for the grower). By contrast with other plant cultivation practices, bonsai is not intended for production of food, for medicine, or for creating landscapes. Instead, bonsai practice focuses on long-term cultivation and shaping of one or more small trees growing in a container.
A bonsai is created beginning with a specimen of source material. This may be a cutting, seedling, or small tree of a species suitable for bonsai development. Bonsai can be created from nearly any perennial woody-stemmed tree or shrub species that produces true branches and can be cultivated to remain small through pot confinement with crown and root pruning. Some species are popular as bonsai material because they have characteristics, such as small leaves or needles, that make them appropriate for the compact visual scope of bonsai.
The source specimen is shaped to be relatively small and to meet the aesthetic standards of bonsai. When the candidate bonsai nears its planned final size it is planted in a display pot, usually one designed for bonsai display in one of a few accepted shapes and proportions. From that point forward, its growth is restricted by the pot environment. Throughout the year, the bonsai is shaped to limit growth, redistribute foliar vigor to areas requiring further development, and meet the artist’s detailed design.
Source : Wikipedia