A duopoly is a market structure in which two dominant companies or firms have control over the production and distribution of a particular product or service. This type of market structure is characterized by a high level of competition between the two companies, often resulting in limited choices for consumers and high prices. In a duopoly, the two companies have a significant influence on the market and can impact the pricing, quality, and availability of the product or service. This can lead to a lack of innovation and diversity in the market, as the two companies may prioritize maintaining their dominant positions rather than introducing new ideas or products. Overall, a duopoly can have both positive and negative effects on the market, depending on the actions and strategies of the two dominant companies.