Ok, Now that you know that it's another way to advertise to your friends, your friends friends, and also many of your family members there are a couple of things that you need to be aware of.
When emailing to some of your friends, friends you want to send to one person, and then BCC or (blind carbon copy) everyone else that's on the carbon copy list. That way they don't see who its coming from unless you put your email address in the body, and you can email a bunch of people all at once, even people you don't even know.
Also when you are going to send out marketing through emails remember to add a tracking link within the email that way you can monitor the results and effectiveness of the email marketing. You can use Aweber, or Get Response for a very inexpensive price to help with that.

Hope this helps.