A more thorough explanation:

A secondary offering is when someone who bought a security in a primary offering sells it to another person. This means that the issuer of the security does not receive any money from the sale.

For example, if a company sells shares of stock to the public for the first time in a primary offering, and then a few months later, one of the people who bought those shares decides to sell them to someone else, that is a secondary offering.

However, there are some restrictions on selling securities in a secondary offering. If the primary offering was public, then the seller can usually sell their shares freely. But if the primary offering was private, then the seller may not be able to sell their shares unless they meet certain requirements.

Overall, a secondary offering is a way for investors to buy and sell securities after they have already been issued in a primary offering.