Similar to monopoly, oligopoly is a market that is dominated by a small group of large sellers. The difference between oligopoly and monopoly is that monopoly will just have one company control the market, but oligopoly will have several companies compete together. It is a kind of market between monopoly and total competitive market; the behavior of sellers will have effects on other companies. So, businesses in oligopoly will always use game theory: a strategy of decision to decide how to react to others' action and how to maximize profit. An example of this in the computer technology market is the collusion between Apple and Microsoft; these two companies are the ones that dominate the computer sector. In fact, Apple has been reported to have formed an alliance with its rival, Microsoft. As a result, both companies benefit and lead the market, making it difficult for other technological companies to enter this type of market. I need help to get more examples of the rival of Microsoft and apple for my microeconomics course, to add more onto this