The Start Menu is the one feature that has been constant in all the versions of Windows I have used (since Windows 95). It is not supposed to be here (on this list) but since it was taken away forcefully from us in Windows 8 and replaced with the Start Screen we never fully embraced, it’s definitely worth a mention. In Windows 10, unlike in Windows 7 and before, the Start Menu is somewhat extended and extensively customizable. That is mostly thanks to the shrinking of the Start Screen (sort of) in non-touch devices like the laptop I use. There are live tiles and the other tiles in all their modern glory. You can stick with the single strip Start Menu of old (by removing all the tiles) or just go with whatever your computer will boot into.
For the Start Screen lovers, it’s buried deep in the settings app. If you’re on a non-touch device then you’ll never get to interact with it unless you go and enable it. For those on touch devices then it is the default when the device is in use as a tablet thanks to the Continuum feature.