They're not the same, but 2.80 is the first release in the 2.8 series, so this is the release of both the specific 2.80 version and the 2.8 series. Next will be

They're not the same, but 2.80 is the first release in the 2.8 series, so this is the release of both the specific 2.80 version and the 2.8 series. Next will be 2.81, etc. (Except it's not, because it hasn't been released yet. Still in beta.)