Email notification simply allow you to know when people interact with you on Facebook, whether through wall posts, comments, tagged photos or friend requests. Similar to the notifications you see in the lower right hand corner on your Facebook page.
You can setup either you want to enable or not. You have option to modify and setup to manage the settings so that you will only get notification only the things you have select. For example comments only. So, if you have selected comments only then Facebook will send all the comment notification to your email.
Link to Setting up
Well not only this. You will able to get weekly degests notification of your friends with upcoming birthdays, all you need to do is check the boxes you like next to these options. If you do rather not be notified when people poke you or comment on your photos, just leave those boxes unchecked.
So, how you will able to change the email address?
Step 1:Go to your Facebook profile and click Settings tab. You will then see your current email address and can select change to add or delete addresses.
Step 2:Now you can click on add another email address to change the email address.Your Facebook email notifications will only be sent to the address you designate as your "Contact Email," so also be sure this information is accurate.