Changing @me.com to @iCloud.com email address

Help...What does this do? Haven't had much success making use of ICloud. Guess I just don't understand how to integrate it into my Apple group of devices.....iMac early 2009 version, iPad2, IiPhone 3G and iPhone Touch 2nd gen. Before I mess around with my email address, I thought I'd try to understand it first. Thanks.