Also, is it possible for another program to be able to read the file and use it in another wallet that's not mist? Or is it only usable in Mist? Thanks.
1 Answer
It's commonly known as a "keystore file," and it's pretty widely accepted (e.g. by MyEtherWallet, Parity, Geth).
See https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition/b66dfbe3e84287f6fa61c079007255270cd20c14 for an explanation of the file format. (For some reason, the latest version of that page doesn't show the details, hence the link to a previous revision.)