Gmail is Google's email service. Like AOL and Yahoo's email, it can be accessed from any computer by using your password if you have signed up for Google's free services.
One of the neat things that I have found about it is that you can email yourself if you have a file, pictures, etc. that you want to save or have available elsewhere. In addition, the storage is online instead of on your hard drive.
Another thing you can do is link the attachment in your email in your blog or website if you want to share. Here is an example.
