A more thorough explanation:

The secondary market is where investors buy and sell securities that have already been issued. This is different from the primary market, where new securities are issued and sold for the first time.

For example, if a company decides to go public and issue shares of stock for the first time, it does so in the primary market. Once those shares are sold to investors, they can then be bought and sold on the secondary market. This allows investors to trade securities with each other, without the involvement of the issuing company.

Other examples of securities that can be traded on the secondary market include bonds, options, and futures contracts.

The secondary market is important because it provides liquidity to investors. If an investor needs to sell a security, they can do so on the secondary market, rather than waiting for the issuing company to buy it back. Similarly, if an investor wants to buy a security, they can do so on the secondary market, rather than waiting for a new issue to become available.