Oligopoly is a market with few sellers. Oligopoly is a market where a few dominant sellers sell differentiated or homogenous products under continuous consciousness of rival’s action.

The oligopoly market is concerned with group behaviour, and there are two types of oligopoly:
• Collusive oligopoly
• Non-collusive oligopoly

Non-collusive oligopoly includes three models:
• Cournot’s model
• Stacklberg’s model
• Kinked demand curve

Collusive oligopoly includes:
• Centralized cartels
• Market sharing cartels
• Price leadership

There are three types price leadership:
• Price leadership by low cost firm
• Price leadership by a large dominant firm
• Barometric Price leadership