Scared to try to use NS and vhosts

I’m sorry, it simply doesn’t make sense to me, but I’m basically ignorant anyway.
That vhost selector list under shared folders lists server aliases from dns it seems… why, what’s the point, the intended function?
I don’t see how it relates to vhosts as I understand them, now that I have no server aliases and have populated the hosts and now have a working vhost system. idk what’s going on really, so I have nothing to offer.