What does it mean when..?

What does it mean when if you're updating your booking online and want to select your seats, but nearly all seats are grey apart from the odd single seat?!
Does it mean that all the other seats are taken, or is it a case of when you check in you'll be able to get two together?!
Also, what's the deal with an X fare.. is it upgradable using miles and such?
so many questions.. well two.
Does it mean that all the other seats are taken, or is it a case of when you check in you'll be able to get two together?!
Also, what's the deal with an X fare.. is it upgradable using miles and such?
so many questions.. well two.