Self-publishing is basically the publishing of books and various other media personally by the authors themselves. In other words they are not published through any agents or publishers.
Self-publishing in practical terms represents a very small portion of the book publishing business in terms of total sales. Self-publishing has been there in one or the other form since the establishment of publishing. It has experienced a raise in its activity with the development of various publishing technology. The development includes desktop publishing systems, xerography, the World Wide Web and print on demand.
The best part regarding self-publishing is that there is no barrier to age and the writer has the freedom to set their own price. The writer controls everything starting from editing to formatting.