Monopoly: A monopoly is when one company has exclusive control over a product or service in a particular market. It's like if only one student had all the candy at school - they could set any price they wanted because no one else was selling candy.
Corporation: A corporation is a type of business that's legally considered an individual entity separate from its owners. It's like if your school club was considered its own person with rights and responsibilities.
Trusts: Trusts are arrangements where one party holds property for the benefit of another party. In terms of big business, this often means consolidating several companies under one board of directors to control competition - kind of like forming an alliance in a game to ensure you win.