Market share is typically reported as a percentage and reflects the portion of a target market that is an actual customer base. A "market" is a universe of customers or clients who are interested in a particular product, service, or company. An increase in market share often makes economies of scale available that can contribute to earnings and profit margins. Generally speaking, most businesses seek to increase their market share.
Market share may be reported as revenue or unit sales from a specific market divided by the total possible revenue or unit sales in that market. Because the figure for the possible / available revenue or unit sales in a specific market must be estimated or extrapolated, it is common for a firm to use market research to arrive at that figure.