Back to My Mac puts any Leopard-based Mac you use within easy reach. .Mac finds your remote Mac computers over the Internet and displays them in the Leopard Finder on the Mac you're using. So you can connect from anywhere with just a click.
With screen sharing, you can control your remote Mac as though you're sitting in front of it. Edit and save documents, launch applications, move folders. You can be anywhere in the world and feel like you never left.
Say you're making a presentation on your Mac at work but need a photo from your Mac at home. Simply select your remote Mac in the Finder sidebar and connect. You can browse your entire hard drive and drag the file you need to your local Mac.