Wear OS - definition
>Wear OS, formally known as Android Wear, is Google's OS for smartwatchs and other wearables.
Wear OS by Google works with phones running Android 4.4+ (excluding Go edition) and iOS 9.3+.
Wear OS supports NFC, Bluetooth, GPS and wrist Heart Rate Monitors. However, not all manufacturers choose to support all features.
For more information visit wearos.google.com