Google really wants the apps you use to take the context of where you are into account. Thus Nearby, a feature that uses Bluetooth and your device's GPS to deliver you apps based on where you are. The post on Google's official Android blog gives a few examples of how this might work: printing photos directly from your phone when you're in a CVS Pharmacy or using the Mobile Passport app to duck the customs line at certain airports.
The feature is baked into an update to Google Play Services that's rolling out now and works on devices running KitKat and up; all you really need to do here to use Nearby is have Bluetooth and GPS activated. Much like physical web beacons, you'll receive a notification when you're in proximity to one of the Nearby apps and if you'd rather not check it out, you don't have to.