If you pay a merchant, and the merchant claims to not have received the funds, you may need to prove to a third party you did send the funds - or even to the merchant, if it is a honest mistake. Monero is private, so you can't just point to your transaction in the blockchain, as you can't tell who sent it, and who received it. However, by supplying the per-transaction private key to a party, that party can tell whether that transaction sent monero to that particular address. Note that storing these per-transaction keys is disabled by default, and you will have to enable it before sending, if you think you may need it:
Important commands: "welcome" - Show welcome message. "help all" - Show the list of all available commands. "help <command>" - Show a command's documentation. "apropos <keyword>" - Show commands related to a keyword. "wallet_info" - Show wallet main address and other info. "balance" - Show balance. "address all" - Show all addresses. "address new [<label text with white spaces allowed>]" - Create new subaddress. "transfer <address> <amount>" - Send XMR to an address. "show_transfers [in|out|pending|failed|pool]" - Show transactions. "sweep_all <address>" - Send whole balance to another wallet. "seed" - Show secret 25 words that can be used to recover this wallet. "refresh" - Synchronize wallet with the Monero network. "status" - Check current status of wallet. "version" - Check software version. "exit" - Exit wallet. "donate <amount>" - Donate XMR to the development team.
In this example you're viewing the balance of your primary account (with index `[0]`). `Balance` is your total balance. The `unlocked balance` is the amount currently available to spend. Newly received transactions require 10 confirmations on the blockchain before being unlocked.
`monero-wallet-cli` is the wallet software shipped in the Monero archives. It is a console program, and manages an account. While a bitcoin wallet manages both an account and the blockchain, Monero separates these: `monerod` handles the blockchain, and `monero-wallet-cli` handles the account.
Pass in the transaction ID you want the key for. Remember that a payment might have been split in more than one transaction, so you may need several keys. You can then send that key, or these keys, to whoever you want to provide proof of your transaction, along with the transaction id and the address you sent to. Note that this third party, if knowing your own address, will be able to see how much change was returned to you as well.
Payments made to an integrated address generated from your account will go to your account, with that payment ID attached, so you can tell payments apart.
