A more thorough explanation:

A shelf offering is a type of public offering of securities where the issuer can make multiple offerings based on the same prospectus, known as the core prospectus. This means that the issuer can offer securities whenever they want to take them down from the shelf, without having to file a new registration statement with every offering.

For example, if a company wants to raise money by issuing stocks, they can file a core prospectus with the Securities and Exchange Commission (SEC) and offer a portion of the stocks to the public. Later on, if they want to issue more stocks, they can do so without having to file a new prospectus. This saves time and money for the issuer.

Shelf offerings are only available to seasoned issuers and well-known seasoned issuers. These are companies that have a track record of filing timely and accurate reports with the SEC.

The main advantage of shelf offerings is that they provide timing and certainty to the issuer. They can issue securities when market conditions are optimal, without having to wait for extensive SEC review after they file their core prospectus. The core prospectus also prospectively incorporates by reference the issuer’s periodic reports, meaning the issuer does not need to amend the core prospectus in the event of material developments.

However, it's important to note that Section 11 still applies to subsequent issues in a shelf offering. This means that the issuer must be sure that any material developments are included in disclosures incorporated by reference or file a supplemental prospectus.