Proprietary trading is a term used in the context of a bank or other financial institution wherein the bank or financial institution engages in trading stocks, futures, options, commodities, currencies & other derivative instruments with its own money & on its own account.
Traditionally banks & other financial institutions are engaged in accepting deposits from clients & lending the same at a higher rate to earn an income equivalent to interest rate differentials. Also Investment banks have played a major role in fund raising for its clients. Investment Banks also play a big role in helping their clients to find the buyers for stock issues. Banks have been acting as a guarantor many times for buying the shares of their clients in case the stock issue is under subscribed. Many banks also provide portfolio management services & trading facilities to their client. While providing all these services the bank or other financial institution is engaging in trading on behalf of their clients for which usually it charges fees or commission to the clients.