Hallmarks of an offering include the following (though none are an absolute requirement in every circumstance): Rounds are often described according to the nature of investors, the size of investment, and the stage of the enterprise.
Because there are no public exchanges listing their securities, private companies meet venture capital firms and other private equity investors in several ways, including warm referrals from the investors' trusted sources and other business contacts; investor conferences and symposia; and summits where companies pitch directly to investor groups in face-to-face meetings, including a variant known as "Speed Venturing", which is akin to speed-dating for capital, where the investor decides within 10 minutes whether s/he wants a follow-up meeting.
Rounds may have one or more lead investors who negotiate and enforce the terms of the agreement.
These are usually the parties with the greatest sophistication, resources, reputation, and/or connection to the investment.
One other distinction is between public offerings for public companies, which are widely advertised and subscribed, and private offerings made by private companies, which have strict limits on the number and nature of the potential investors.