These are the shareholders of the IPO who are selling shares at the time of the offering. The front cover of the prospectus indicates the total amount of shares being offered. The identities and breakdown of shares sold are detailed within the prospectus. The prospectus will also indicate whether shareholders will be selling on the Green Shoe. Investors should be skeptical of any IPO in which shareholders are selling large amounts of stock. Always ask the question "Why are they selling when they want me to buy?"