Types of Companies
Proprietorships are simple mom and pop stores with one owner.
Partnerships are like Ben and Jerry's. Two people that own a business that share the profits and debt.
Corporations are large companies that are lead by a board of directors. They are made up of multiple people, but they have the same legal status as a single person. They can raise large sums of money very quickly due to the number of people that contribute through stocks.
Sean bought stock in Ford when it was cheap a few years ago. The price of that stock went up so Sean made some money. Then there was a major recall and a Congressional inquiry that lead to a major sell off. Suddenly Ford stock cost half of what it did when Sean bought his shares. That means that Sean has lost money. Although he is a technical owner of Ford he can't tell them what to do. The company almost always owns 51% of more of their company so they stay in control.