An Initial Public Offering (IPO) is the process through which a private company becomes a public company by offering its shares to the general public for the first time. This involves the company issuing new shares to raise capital and allowing existing shareholders to sell their shares to the public. The IPO marks the transition from a privately held company to a publicly traded one, and the shares are typically listed on a stock exchange. Investors can then buy and sell these shares on the open market.