Why is it that some e mails I receive come into my i cloud account folder and others into my "normal" e mail account address? What decides where they are directed?
Welcome Thomasp, it seems that you are given another email address when you register with iCloud. Probably ********@me or something. I noticed this with my sister. I asked why she had changed her email address but knew nothing about it. I guess some of your friends noticed and sent to the @me and others to your old but still current address. I am sure somebody else can confirm this for you.
Yes, and iCloud account comes with a free email address. If you do not want to use it just go to Settings > iCloud and turn off Mail (and other services taht you don't want). This will not affect other accounts that you've set up under Settings > Mail, Contacts, Calendars. Note that your iCloud account also shows up under Mail, Contacts, Calendars. Turning off series in either place will work, but I recommend signing into (or out of) your iCloud account int he Settings > iCloud area.