By the end you will know exactly what changes the day you trade from your own wallet on a contract instead of inside an exchange's building, and which venue fits which job.
Every trade in this act so far happened inside a building. A broker, an exchange, a company: someone's rules, someone holding your coat at the door. If you did our Web3 course, you already know the custody plumbing behind that door: on an exchange, your assets sit in their building.
Today you step outside. On the open market square, the venue is a smart contract, and the coat stays on you. This lesson is not about who holds the assets. It is about how trading itself feels different out here, the day you press swap from your own wallet.
Inside the building, a trade is a note in the house ledger: instant, free feeling, sometimes filled in pieces, sometimes pending for hours. On the square, your trade is a transaction on a public network. The network does real work to process it, and that work costs a fee: gas.
Gas pays for the attempt, not the outcome. If your swap fails, the fee is still gone, because the machines still did the work of trying. And settlement is all or nothing: the whole swap happens in one move or none of it does. That property has a name: atomicity.
Here is the board we will build all lesson: the building on one side, the square on the other, lighting up one difference at a time. The first row is execution. Same intention when you press buy, a completely different machine underneath.
Notice what disappears on the square. No pending limbo, no partial fills, no order sitting overnight in a queue. Your swap is one atomic move: it lands whole or it does not land at all.
On the square, nobody asks you to confirm a final price, because the price can move while your transaction travels. Instead you pre-authorize the worst price you will accept. The allowed gap between the screen price and your worst case has a name: slippage tolerance.
The setting IS the risk decision. Set it tight and a thin market rejects your trade. Set it loose and the whole gap is yours to lose. Who's paying? Loose slippage pays whoever fills you at the very edge of your tolerance.