Unlike the original Galaxy Gear, which has a full build of Android 4.2.2 on board, the Gear 2 and Gear 2 Neo are running the Tizen OS - an open-source OS Samsung played a big hand in developing. That's good and bad, of course. It's great for those who have been waiting to see Tizen on a mainstream product (insofar as smartwatches are mainstream, we suppose) and bad for the tinkerers. That's also led Samsung to drop "Galaxy" from the product name.
I don't care much about the Gear, but I like that Samsung is finally using Tizen for something.