It’s far beyond the scope of this website to address the history and Lore behind the Ultima series.
Take a trip over to Ultima Aiera.
I think the best way is to just play the original games. It will give you a lot more meaning. It’s highly recommended that you at least start at Ultima IV, if you are unable to start from I.
(Feb 26: We apologize: we had to temporarily remove much of this section as the images did not make the migration over to the new server – we’ll be placing them online sometime soon)