Do a search in Help and Support. There are a bunch of MS Knowledge Base articles which explain what it is and how it works. Fundamentally, it is the means by which you can allow a remote commuter to check out your machine and software so that sound technical advice can be given to you. You must grant permission for that remote user to access the account and hence to access your machine. If you ever expect to seek online support (via Microsoft or some other of the support groups which have the capacity for this), you probably would want to keep it so that the support tech could directly access your computer to determine what is wrong.