Final answer:
Market share refers to the percentage of a market accounted for by a specific firm, product lines, or brands.
Step-by-step explanation:
Market share refers to the percentage of a market, defined in terms of either sales units or revenue, accounted for by a specific firm, product lines, or brands. It is a measure of a company's competitiveness and market presence. For example, if a company has a market share of 25%, it means that it controls a quarter of the total market.