The smart contract is a small program that holds funds given to it and sends it to an address only when specified conditions occur.
- Do I have to write the code.?
You can if you want. Else we will have published and verified Dapps which will provide all services that most people want. You can then use these readymade contracts. For example, you need an escrow service you go to a Cardano Escrow app and invite your business partner there and tell him to pay the escrow amount to your instance of a smart contract template. Once he pays it the program will now release the money only if there are the same inputs from both of you, either to return the money to your partner's wallet or pay you for the services you provided. The software will not let a single person to withdraw.
- Where are the details of the contract kept and displayed?
The working part of the contract will live in the blockchain(node). People will interact (for example request for releasing a security deposit of a contract ) through a website/mobile app etc. The details of the contract will also be available on these sites or mobile apps.
- Where would the payment then sit once received?
Each contract has its address where it can receive payment. Only if a specific condition is a meet that money held by contract comes out. When the conditions are satisfied the program will permit the transfer to a wallet satisfying the laid down condition.