Guild Wars 2

I will be buying the Ultimate Edition but I have a few questions regarding the following statement:

“Guild Wars 2: Heart of Thorns expansion (includes Guild Wars 2 core game)”

If it includes the core game is that a separate digital key code?

All I want is the expansion as I already have the core game and if it is a separate key am I able to give that key to a friend – which won’t impact the HoT digital key code I wish to use on my account?

Or is it simply a 1 massive download that doesn’t let you avoid downloading the entire core game again?

Sorry for so many questions but it’s kind of confusing…

There’s no separate key if you already own the base game.