All listings expire when the expiration date for that listing is passed. After a listing expires there is a time period after listing expiration where the listing will be archived. You determine the expiration for classifieds using the "listing duration" chosen when the classified ad was created. Classified ads can be renewed which essentially resets that end date for that listing. You control the duration of listings (and classified ads specifically) using the listing duration feature choices. This support wiki page explains the options for listing duration choices.
Additionally for auctions the duration can happen at a specific date set while placing the auction. Auctions can also be ended with a buy now feature. If this happens the "end date" is set for that time. This starts the "viewable 30 days after expiration" and the "time till archiving" periods from that time.
Classified ads only expire only by set durations or when the user "manually ends" them. If the client manually ends a classified ad the classified ad is archived at that time.
Nothing happens to the listing's data at that moment. All information attached to the auction or classified ad is still within the system. The only difference with expiration is that the listing does not display on the client side any longer. The original user that placed that listing will find that listing within their "expired listings" admin tool if they wish to review, renew or copy it. Classified ads cannot be viewed on the client side once expired. But auctions can still be viewed on the client side for 30 days (or until archived) after expiration. But note expired auctions can only be viewed if they are linked to directly as they do not display in category browsing, searches or modules on the client side.
The next "change" for a listing after expiration is at archiving. With archiving much of the information for the listing is compressed and the images and files attached to that listing are removed from the system. Once archived a listing cannot be truly renewed. You can copy that listing but since most of the associated data has been removed or compressed that data will need to be recreated for any listings created from that archived listing.
You can control the amount of time after expiration before a listing will be archived through the following admin tool setting:
LISTING SETUP > GENERAL SETTINGS > Archive Listing
and if you do not want even archived data to be kept within the system you can set this:
LISTING SETUP > GENERAL SETTINGS > Remove Archived Listings
Note that a listing can be set to archive within the "renewal period" configuration as set here:
LISTING SETUP > GENERAL SETTINGS > Renewal Period
But note that once a listing is archived it can't be renewed.
After a listing has been archived it will still appear in expired listing lists of the admin tool and client side. In the archived state the listing causes little issues in the system as most of it's data has been removed. But if you wish to remove what's left of the archived listing from the system completely you can do so through this setting:
LISTINGS SETUP > GENERAL SETTINGS > Remove Archived Listings
This setting is for how long after a listing has been archived, before it is totally removed from the system. Default is "0 seconds", when set to 0 seconds the feature is disabled, so that no archived listings will be removed. For high traffic classified sites, we recommend setting this to 30-90 days to reduce the database size. For auction sites, we recommend to either keep this disabled, or set really long. Once an archived listing is removed, it can not be retrieved or viewed or "copy to new listing" since it will no longer exist in the system.
In addition, the archived listing information is used for the extra feedback information about a seller. So any listing that has already been completely removed, even the archive of the listing, the feedback will no longer show for that listing, keep this in mind when using this if you run an Auction site. The overall rating will be left intact, but the individual rating values will not be able to be displayed to people viewing the user rating.
This setting applies to all listings irrespective of listing type.