How the strongbox works
Two of three multisig, in plain terms, and the one move that opens it wrongly.
The strongbox that holds your money between paying and receiving is a two of three multisig contract. Understanding it is the difference between trusting the market blindly and knowing exactly what protects you and what does not.
Three keys, any two open it
Every order generates three keys, held by the buyer, the vendor and the market. Any two of the three together can move the coin. In a clean order the buyer and vendor sign after delivery and the market key never moves. The market cannot touch the money alone, because one key out of three opens nothing.
Why three and not two
A straight two-key box between buyer and vendor jams forever if either side goes quiet. The third key is the tiebreaker. Because the market holds only one of three, it cannot walk off with deposits, which is the exit-scam that has sunk weaker markets. It can only help resolve a dispute.
The dispute path
When something goes wrong, a moderator reads signed evidence from both sides and co-signs with whichever side is owed. That co-signature is the second of the two needed, and the coin moves accordingly. A refund co-signs with the buyer to a refund address. The vendor is not required for a refund to settle.
The one wrong move
Finalising early means signing your release before the package is in your hands. It empties the strongbox to the vendor and removes the dispute path. On an unproven vendor it is the mistake that undoes every other protection. Do not do it, whatever reason is offered.