The public markets are what most people know: this is where stocks like Apple or Amazon may trade daily on exchanges with "live" prices and strict reporting rules. The private market is an estimated $20 trillion* universe where companies like SpaceX or Stripe grow for many years before possibly going public. In the private market, information is less available, pricing is negotiated, and transactions may be subject to restrictions like company approval, ROFRs.
*Source: Preqin data via
Institutional Investor (2024).