.A stock broker or stockbroker is a regulated professional broker who buys and sells shares and other securities through market makers or Agency Only Firms on behalf of investors.

A transaction on a stock exchange must be made between two members of the exchange — an ordinary person may not walk into the New York Stock Exchange (for example), and ask to trade stock. Such an exchange must be done through a broker.
There are three types of stockbroking service.
* Execution-only, which means that the broker will only carry out the client's instructions to buy or sell.
* Advisory dealing, where the broker advises the client on which shares to buy and sell, but leaves the final decision to the investor.
* Discretionary dealing, where the stockbroker ascertains the client's investment objectives and then makes all dealing decisions on the client's behalf.
The term Trader can refer to:
* Merchant, retailer or one who attempts to generally buy wholesale and sell later at a profit
* Trader (finance), someone who buys and sells financial instruments such as stocks, bonds, derivatives, etc.
* Trader Classified Media, classified advertisement company
* Trader Media East, largest classified advertising company in Central and Eastern Europe .In finance, a trader is someone who buys and sells financial instruments such as stocks, bonds and derivatives.
A broker who simply fills buy or sell orders is not a trader, as they are merely executing instructions given to them. Traders are either professionals working in a financial institution or a corporation, or individual investors, or day traders. They buy and sell financial instruments traded in the stock markets, derivatives markets and commodity markets, comprising the stock exchanges, derivatives exchanges and the commodities exchanges. Several categories and designations for diverse kinds of traders are found in finance, these may include:
* stock trader
* day trader
* pattern day trader
* swing trader
* floor trader
* rogue trader