Depends which promotion you select , there are 2 types.
The General Promotion campaign you pay that % selected, only when the item sells.
The Advanced / Priority Campaign strategy you pay for any clicks your item receive on viewing. This one can really rack up a lot of listing fees!
eBay say....when you promote your listings using a priority strategy, your campaign will use a cost-per-click (CPC) model. You’ll only pay for clicks on your ads and the cost for each click is based on a second price auction, which means the fee charged will be determined by factors like listing quality, keyword relevance, your bid amount, competition from other sellers, and a reserve price (the minimum amount we've determined a click is worth, taking item quality, competition, seasonality, and marketplace thresholds into consideration).
@johnnsue1