A contribution to the capital needed by a firm, by virtue of which the shareholder becomes a part owner of the firm in perpetuity. A share certificate is issued, entitling the shareholder to a dividend . This will normally be paid once or twice a year and will vary depending on the profits earned during that year. (In a very bad year it may be zero.)
Shares in a public limited company can be sold on the Stock Exchange but the price will be uncertain and will depend on expectations of future profitability or likely growth in the share price. Some high-technology shares, e.g. Microsoft, seldom pay dividends but may offer some prospect of capital gains due to a rising share price.
Shares in a private limited company can be sold with the permission of the rest of the shareholders.