The process by which a company files required documents with the Securities and Exchange Commission detailing the particulars of a proposed Public Offering. A company issuing shares must reveal essential facts and detailed information about its business during the registration process, including a business and asset description, a description of the security being offered and the details of that offering, a description and names of the company’s management, and the company’s financial statements, which have been certified by an accountant working independently of the company. – Source: Investopedia.com
In terms of an IPO, the period where an issuer is subject to a SEC ban on promotional publicity. The quiet period usually lasts either 40 or 90 days from the IPO. – Source: Investopedia.com