The real wordsTheory
The secondary market
Secondary equity marketAllows investors to sell stocks they previously purchased to other investors. It is the source of liquidity for equity.
Prof. Panda's version is sharper: already issued stocks are bought and sold between secondary buyers and sellers through the exchange mechanism, and the original issuing firm is not involved.
He also gives the consequence of liquidity's absence: without it, the owner would be forced to hold a debt instrument until it matures, and an equity instrument until the company is voluntarily or involuntarily liquidated.