A marketplace sells nothing of its own. The working marketplace definition is a business that puts independent sellers in front of buyers on one storefront, runs the transaction between them, and earns a commission rather than a margin on stock. The seller keeps the inventory risk and, in most models, the contract with the buyer.
The cold-start problem every operator has to solve
Supply without demand is worthless to sellers, and demand without supply sends buyers away for good. Almost every marketplace that works solved one side first in a deliberately narrow space — one city, one category, one professional niche — where a few hundred listings were enough to make search useful.
Density is the real product, and founders asking what is marketplace liquidity are asking about exactly this. A buyer who searches twice and finds nothing does not come back, and the sellers notice before the operator does.
How does a marketplace work in practice
The operator owns discovery, ranking, the trust layer of reviews, vetting and dispute handling, and the payment flow. It does not own the goods, set the seller's cost base, or usually control fulfillment. That is what keeps the cost of growth low compared with a retailer, and what makes quality control so hard.
A platform is the wider software category this sits inside. Every marketplace is a platform, but plenty of platforms have no shared storefront at all.
The money flow decides the licence
The everyday marketplace meaning stops at the storefront; the operational one starts with the money. Two structures dominate. Under gross settlement the buyer's full payment lands with the operator, which pays sellers afterwards; under net settlement or a split payment the provider divides the money and pays each party directly. That one choice decides whether the operator needs a payment authorization of its own — the opening question of marketplace compliance — and whether it can withhold a seller's cash while a buyer complains.
Take rate and the point where sellers leave
Commission has to be low enough that sellers stay and high enough to fund the acquisition of the buyers they came for. Sellers with strong repeat custom do the arithmetic quickly: once they can reach the same buyer directly, the take rate is a tax on a relationship the marketplace no longer supplies. Operators defend that edge with payment protection, logistics or financing — anything a seller cannot cheaply replicate.
What a buyer checks when a marketplace changes hands
Repeat purchase rate, seller concentration, and how much order value arrives without paid traffic behind it. Then the unglamorous half: whether sellers were verified properly at vendor onboarding, and whether the payment structure survives a change of ownership or has to be rebuilt on day one.