An oligopoly is a market where there are very few suppliers, and competition is very limited since the barriers to entry are very significant.
For example, the automobile industry is an oligopoly. There are only a few car manufacturers in the world, and they all are very large corporations. It costs hundreds of millions of dollars to introduce a new car model, and every time that happens, the corporations must carry on expensive advertising and promotional campaigns.
A wholly-owned subsidiary is a corporation with a common stock owned by another company at one hundred percent (100%). When a company owns less than fifty percent (50%) of another company, the company holds a minority interest in it. The parent company will control all development, management, and profits with a wholly-owned subsidiary but it also shares costs and responsibilities.