You can always see your own deleted answers if you visit the page again (except in the few rare occasions of a hard delete). Deletions are by default soft deletions, meaning the content remains, but is invisible to all except

- the owner (in case of answers, deleted questions are visible only to the following groups)
- users with `>= 10k` rep
- moderators
- developers

Those who can see the content can vote to undelete it. Votes to undelete self-deleted answers by the author are binding, as are moderators' and developers' votes. For ordinary high-rep users, it requires three undelete votes (in general), but moderator-deleted content can only be undeleted by moderators and developers.

Comments, on the other hand, are really gone when deleted, though not totally. Moderators (and developers) can still [see][1] them (but they are not shown to them by default, in contrast to deleted answers that are visible to them and 10k+ users automatically), but not even moderators can [undelete them][2] (developers presumably can).

[1]:http://meta.stackexchange.com/questions/85442/allow-moderators-to-see-deleted-comments
[2]:http://meta.stackexchange.com/a/98037/177145