1. Financial markets.
The market for the trading of securities that have previously been bought by investors as new issues in the primary market.
2. Loan markets.
In relation to loans, the market in which loans are traded between the original lenders and subsequent lenders.
The existence of secondary markets is one of the features that makes primary investors willing to invest in primary markets by buying assets or making other forms of primary investment.
The fact that secondary markets are present means the primary investors will be more likely to be able to exit their investments readily at a time of their choosing.
Especially if the relevant secondary market is deep and liquid.