There are a number of methods that "work" to varying degrees. For bluetooth, stores can install ble beacons that a phone app can detect (if it has permission) a

There are a number of methods that "work" to varying degrees. For bluetooth, stores can install ble beacons that a phone app can detect (if it has permission) and then get a rough estimate of the general area in the store you are in. For wifi, stores can detect your phone's probe requests to estimate your location. If you are not associated to the store's wifi network your probe requests will use a randomized mac address (at least with ios and pixel devices). This means they probably won't be able to identify you as a new vs returning customer. Stores also use cameras to track path traversal throughout a store. These paths are difficult to tie to an actual identity so are generally used in aggregate and not for more targeted marketing.