The game has check points (designated by 1-1, 1-2, 1-3, 2-1, 2-2, 2-3... etc within the aesir teleport menu/multiplayer menu). If you save and quit it will bring you back to the last check point designated by one of these markers that you last crossed.
If you want some sort of indication that you crossed such a check point (any time you receieve a new token, viewable in the stats page within the start menu), you have crossed a check point that you can start at.
Hope that helps explain things.
Also note that when you cross a check point, the game will save automatically (the game will also do this when looting obelisks as well), but if you just entered a new room / area and see "saving" flash on the bottom right of your screen, check your stats page to see if a token showed up.
Tokens are multi purposed. Tokens are cashed in after a boss fight ( if you have all of your tokens for a given level / world ) for better boss loot, aka, the good stuff
.
Once you have cashed in your tokens for a specific world / level, the next time you replay that level your tokens will be reset and you will have to re-accquire them. If you re-accquire a token you already have (by replaying a section of a level repeatedly for example) you will still hit the checkpoint, and its effect of that being the last place you have been. Saving and quiting while you are not in campaign mode however functions differently and to tbe best of my knowledge has no effect on where you will begin next for when you next continue with your campaign.