A two-sided marketplace serves two interdependent user groups whose value to each other grows with participation. Airbnb (hosts and guests), Uber (drivers and riders), eBay (sellers and buyers), and Upwork (clients and freelancers) are canonical examples.
Marketplaces face a cold-start problem (neither side joins without the other), liquidity challenges (matching supply and demand quickly), and disintermediation risk (users transacting off-platform after meeting on-platform). The take rate captures the platform's claim on each transaction.