An angel investor (also known as a business angel, informal investor, angel funder, private investor, or seed investor) is an affluent individual who provides capital for a business start-up, usually in exchange for convertible debt or ownership equity. Angel investors usually give support to start-ups at the initial moments (where risks of the start-ups failing are relatively high) and when most investors are not prepared to back them. A small but increasing number of angel investors invest online through equity crowdfunding or organize themselves into angel groups or angel networks to share investment capital, as well as to provide advice to their portfolio companies. In the last 50 years the number of angel investors has greatly increased.

Venture capital financing is a type of funding by venture capital. It is private equity capital that can be provided at various stages or funding rounds. Common funding rounds include early-stage seed funding in high-potential, growth companies (startup companies) and growth funding (also referred to as series A). Funding is provided in the interest of generating a return on investment or ROI through an eventual exit such as a merger and acquisition, (also referred to as M&A), or Initial public offering, (commonly known as an IPO) of the company.

Series B financing (also known as series B round or series B funding) is one of the stages in the capital-raising process of a startup. Essentially, the series B round is the third stage of startup financing and the second stage of venture capital financing.

A venture capital firm goes for this round of funding when the company has proved its mettle and is a success in the market. The company goes for Series C round of funding when it looks for greater market share, acquisitions, or to develop more products and services.

Seed money, sometimes known as seed funding or seed capital, is a form of securities offering in which an investor invests capital in a startup company in exchange for an equity stake or convertible note stake in the company. The term seed suggests that this is a very early investment, meant to support the business until it can generate cash of its own (see cash flow), or until it is ready for further investments. Seed money options include friends and family funding, seed venture capital funds, angel funding, and crowdfunding.