Lots of people know what monopoly is because of the board game. The point of the game is to get the most properties and the most money. Part of that is getting “monopolies,” which are all the properties of one color. A monopoly in the economic world is similar- it’s one company that has a large amount of control over a product or service with very few alternatives and substitute goods available. Monopolies in the United States are only legal if the government grants them; patents, trademarks, and copyrights are all technically monopolies.
The question of the legality of monopolies is part of the reason that states like Pennsylvania allow you to compare prices for where you get your electricity from. If you can compare prices, you are able to get the best deal possible and you aren’t being controlled by having to buy your energy from a certain company.
Oligopolies are similar to monopolies, but it’s where a product or service is controlled by a certain number of entities. Many people assume that Comcast is a monopoly, and to an extent, they are to cable. But because Dish Network, Verizon FIOS, and DirectTV all have a presence in many areas, they aren’t (also, the FCC has different rules over communications companies, but that doesn’t matter for this discussion). These 4 companies are an oligopoly. There are other smaller companies that have smaller shares, but these companies control the majority of the market, controlling prices and supply and demand.
Now, oligopolies can function in two directions. On one hand, oligopolies can be great for consumers because they’re so competitive that it keeps prices low and accessibility high. On the other hand, if the members of the oligopoly work together, they may drive prices up and hurt consumers.