So according to the mouse-over hints, "до" means "until/to", and that's well enough, but what does "свидания" mean? When I mouse over that it just gives me the combined meaning of the two words, ignoring the second word on its own. My guess would've been "later", but according to other comments here, that would be "скорого", so I've got nothin' at this point. lol.
it is literaly: to see you. свидание is randes voux, meeting. just this duolingo do not agree with to see you. why? good bye is not so precise, even the use in english is baxicaly the same as far as i know. strange. (i am just learning russian, but i am in office with many and my native - czech - language is similar as let's say english and deutsch. and well, i speak english quiet a lot in work and private life as well)
до свидания is more formal. You can use it with people you're not on close terms with. пока is informal and you can use it if you have (or plan to make) any close Russian friends. They both mean the same thing: Bye/Goodbye. I'm not a native Russian, but I think до свидания literally means "until our next meeting."