Both terms refer to the Elizabethan idea of what happens after you die. If you are admitted to heaven, your spirit rises upward to God - and you are "saved" (a word with the same root as "salvation"). If you are sent to hell, you descend below the earth to a fiery pit: and you are "damned".
"Salvation" and "damnation", then are simply opposites: and characters like Dr. Faustus expressly fear being "damned" if they blaspheme or do something against God (of course, Faustus is actually sucked down to hell at the very end of Marlowe's play!). What a religious character would hope for, conversely, is salvation - and the forgiveness of any sins they had committed, as per John 3:16:
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
More complicated is how you earn salvation or damnation. This one depends which Christian from which age you ask - and, of course, some Christians believe in "exclusive salvation": if you believe in Jesus, you are saved. If not, you burn in hell.