Apple Watch is a line of smartwatches produced by Apple Inc. It incorporates fitness tracking, health-oriented capabilities, and wireless telecommunication, and integrates with iOS and other Apple products and services. The Apple Watch was released in April 2015,[18][19] and quickly became the best-selling wearable device: 4.2 million were sold in the second quarter of fiscal 2015, and more than 100 million people were estimated to use an Apple Watch as of December 2020. Apple has introduced a new generation of the Apple Watch with improved internal components each September—each labeled by Apple as a 'Series', with certain exceptions.