If beacons are only broadcasters and they can not communicate with iPhone or other devices, How come companies like Estimote, Bluecats provide configurable parameters like Advertising Interval,Broadcasting power etc reflects the change on its battery life. In recent update they are also providing parameters like smart battery saving and basic battery saving ? General answer followed by technical terms will be appreciated.
Bluetooth beacons typically implement broadcast-only standards like iBeacon, AltBeacon or Eddystone which use Bluetooth LE advertising with no two-way communication as you suggest.
However, there is nothing in these standards that says that a hardware device that acs as a beacon can't implement two-way communication for other purposes. And that's exactly what most manufacturers do. They implement a custom GATT service that allows read-write access to configuration parameters inside the beacon. This allows an iPhone, Android device, Mac or Windows PC to make a read-write connection to the beacon device and set parameters like advertising interval as well as the beacon identifiers.
You can see an example of such a GATT service in Google's Eddystone Configuration Service.. This is an attempt to standardize the way you configure Eddystone beacons across manufacturers. Similar non-standard GATT configuration services are used by manufacturers supporting the iBeacon format. Some manufacturers publish these GATT service APIs and some do not, keeping the APIs private only for use inside their configuration apps.