An angel investor is a wealthy person who invests his or her own money in a company—usually a start-up—that is in the early stages of development.
Angel investors expect to take ownership positions in the companies they support because their capital is unsecured—they have no claim on the company’s assets. Their ownership may take the form of equity or convertible debt. They also tend to have clear exit strategies for ending involvement with the business.
The goal of an angel investor is to help businesses get established. Their funding terms are often more favourable than those of other lenders. Many invest to support the entrepreneur behind the business, not just the business itself.
Angel investors may provide a one-time injection of money into a business or invest on an ongoing basis in the company’s fixed assets or working capital.
You can find a comprehensive BDC article on the subject, called How to find angel investors. It includes advice on preparing for your meeting with angel investors and the advantages and disdvantages of working with them.