Secondary market trading is the buying and selling of shares, bonds and other securities among investors after the securities have first been sold by the issuer. The issuer receives nothing from these trades; ownership simply passes from one investor to another at a price set by supply and demand. It follows primary market issuance, in which the issuer raises money by creating and selling the securities. The market as a whole is described under secondary market.
Trading takes place on a stock exchange and other organised venues, where orders are matched in an order book, and over-the-counter, where dealers quote prices directly to clients, as is usual for most bonds. A market maker supports liquidity by standing ready to buy and sell. An active secondary market matters to issuers too, because it provides price discovery and makes investors more willing to buy new issues.