Purpose
Auto Tracking is a tool that is active behind the scenes - for all the items that you look at, Prospector automatically and privately takes note of the sellers and bidders for the listings.
It gathers this information in the hopes that it might lead to the discovery of new items of interest. The assumptions are that sellers tend to sell the same kinds of items, and that the bidders may have tastes that overlap yours. Prospector sorts the sellers and bidders - the more items you've seen of a seller, or the more items you've looked at that have been bid on by a bidder, the higher they rank.
Access
This information is shown through the Auto Tracking button in the Prospector Tools toolbar, or through Tools menu / Auto Tracking.
Two tables are displayed - one for sellers and another for bidders.
The seller links let you see their other items. The bidder links invoke Prospector's Bidder Search for the bidder.
Notes
The Auto Tracking information does not carry over between application runs.