This is the original species from Brazil that modern cultivars (called Begonia Semperflorens-cultorum Group) are derived from. They are often known as bedding or wax Begonia and are classified as annuals, but in frost-free Sydney gardens they will last several years. They are small plants growing 20-30 cm tall, with typical Begonia flowers, and rounded, fleshy leaves that may be green or bronze. Flowers come in shades of pinks, white or red. They bloom over a long period in the Sydney climate - from mid-spring until late autumn, and in warm microclimates may flower all year. They look and do best when grown en masse.
Like other Begonia, they are valuable for shaded areas of the garden, although they also seem to cope with a sunny position. They tolerate dryness very well. They may become leggy at the end of winter: they can be cut back hard in September. They do tend to self-seed but this can be an asset in a shaded border! They are excellent for containers. There are numerous named cultivars. They can be grown from cuttings. They can be subject to mildew - it is best to make sure they have a good flow of air around then to minimise this. A spray of bicarb soda mixed with water can be tried to control any mildew that occurs. They can apparently be grown indoors - I haven't tried this myself.
For more information, visit the very informative website of the NSW Begonia Society.