STR = Sell Through Rate
Jargon for percent of listings over a time period that result in a profitable sale.
High STR = Good Item for Auction/BIN on the floor due to lower Final Value Fee (FVF), but at higher listing fees. Also, makes a good item to attract buyer INTO THE STORE with cross-promotions and appropriate discounts (like shipping).
Low STR = Good Item for Store Inventory due to higher FVF, but lower listing (Store) fees. It can sit in the store without high overhead in fees.
That's a general rule, but there are always exceptions (like seasonal sale items). It really depends on what you are selling, your competition, and your visibility in the market-place, as other contributing factors.
Danno