If the company has never issued equity to the public, an Initial Public Offering (IPO), would be the first sale of stock by the company to the public. Whilst there are many reasons why a company may decide to go public, the main one is the opportunity to access additional capital for use in the business. The company raises this money by issuing either debt or equity in the form of shares.
Other Capital Raisings may involve the issue and sale of securities to a small number of investors instead of the general public. Unlike with a public offering, a formal prospectus does not have be provided for a private placement and thus it is often restricted to experienced or sophisticated investors that have a strong understanding of the process and risks involved.