Series8 is a series of Apple Watch, and s8 is the abbreviation of Apple Watch series8.
Apple, Watch Series8 can be worn on the wrist to provide health monitoring, exercise monitoring and daily life support. S8 is a smart phone, which provides communication, photography, games and other functions. In addition, their operating systems and user interfaces are different. Apple, Watch, Series and 8 run the WatchOS operating system, and S8 runs the Android operating system.