in a few sentences explain the following

What is an oligopoly market?How does it differ from a monopoly and perfectly competitive market?Why can oligopolies earn long-run economic profits?

What is a monopoly, and how does it differ from a perfectly competitive firm?Why can a perfectly competitive firm only earn short-run economic profits, but a monopoly can earn both short and long-run economic profits?

What is the specific difference between economic profits and normal profits?What is the significance of the "break-even" point?