As the name implies, Android Wear is simply a variation of Android specifically tailored to smartwatches. This year’s Wear 2.0 update ran on top of Android 7.0 Nougat, and while some components can be updated through the Play Store, the underlying system can only be updated through normal OTAs.
Google released the Wear version of Android 8.0 Oreo a few days ago, and the update started to roll out to the LG Watch Sport and other models.
Google announces which Android Wear watches will get Oreo update, and which already have it was written by the awesome team at Android Police.