For those who don’t know, Facebook’s custom audience feature, which launched last fall, lets marketers take their current customer lists and show ads to just those people on Facebook. This new addition means they can drill down and only serve ads to desktop or mobile users that have shown interested by actively accessing a given site or app. Facebook offers the following example: For instance, a bike retailer could reach people who started designing bikes on its website but didn’t make a purchase. Through custom audiences, the company can reach these people via desktop News Feed and encourage them to finish customizing online. Or, a mobile travel app can deliver ads to people who have downloaded their app but haven’t used it in a while and encourage them to book getaways within the app. Custom audiences work with all of the Facebook’s ad formats and targeting capabilities, while mobile app custom audiences are similar but designed specifically for mobile app developers. In short, today’s move is yet another example of the company pulling the information on other properties where its plugins reside back to its main service, to the benefit of its revenue-generating partners. Get the full story at The Next Web and Facebook