What’s Bing Rewards? It is Microsoft’s way of thanking you for using Bing search - which, as you may know, isn’t immensely popular, not even among Windows Phone users (who have Bing as the default search app). Bing Rewards allows you to earn credits just by searching with Bing. These credits can be redeemed for gift cards (from Xbox, Amazon, Skype, Dominos or Fandango), or they can be donated “to a local school or charity of your choice.”
According to Microsoft, almost all of the features available with Bing Rewards on PCs will make their way to the mobile version over the next few months.
At the moment, Bing Rewards is available only in select markets (including, of course, the US). To start using it on your Android or iOS phone / tablet, point your mobile browser to the first source link below (you can sign in using your Microsoft or Facebook account).
source: Bing Rewards via Bing blogs