Angel investors are also referred to as business angels, informal investors, angel funders, private investors, or seed investors and are affluent investors who provide capital for business start-ups, usually in exchange for convertible debt or ownership equity. Many angel investors invest online through equity crowdfunding or organize themselves into angel groups or networks to share research and pool their investment capital, as well as to provide advice to their portfolio companies.

The term angel originated from Broadway theater, where it was used to describe wealthy individuals who provided money for theatrical productions that would otherwise have had to shut down. William Wetzel of the Center of Venture Research pioneered the term angel in 1978 in defining the term for investors who supported entrepreneurs raising seed capital ...