A joint stock company is a special kind of partnership. Such a company has a common capital called the stock. The partners in the company are called shareholders, since they receive shares for their contributions to the stock. Shares express ownership interest and decision making power in the company, and shareholders are free to transfer their shares to someone else without needing consent of the other shareholders. While a normal partnership also has ownership interest, the difference is that in a partnership, interest can only be transferred to someone else if all the partners agree to it.

A share also represents how much of the profit each shareholder receives. Since a joint stock company is not necessarily a corporation, a share also represents how much of the loss each shareholder is liable for. As an example, a shareholder holding a 20% share in the company would receive 20% of the company's profits but would also be liable for 20% of the company's debt if it could not be satisfied with company funds.

A for-profit corporation is a joint stock company, except that the shareholders have no liability towards the corporation's debts.