A stockbroker is an individual or company that buys and sells stocks and other investments for a financial market participant in return for a commission, markup, or fee. In most countries they are regulated as a broker or broker-dealer and may need to hold a relevant license and may be a member of a stock exchange. They generally act as a financial advisor and investment manager. In this case they may also be licensed as a financial adviser such as a registered investment adviser.

Stocks consist of all the shares by which ownership of a corporation or company is divided. A single share of the stock means fractional ownership of the corporation in proportion to the total number of shares. This typically entitles the shareholder (stockholder) to that fraction of the company's earnings, proceeds from liquidation of assets, or voting power, often dividing these up in proportion to the amount of money each stockholder has invested. Not all stock is necessarily equal, as certain classes of stock may be issued, for example, without voting rights, with enhanced voting rights, or with a certain priority to receive profits or liquidation proceeds before or after other classes of shareholders.