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.
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.)