What you read means that you have 2 options to update your Windows XP installation :
1. User automatic update. This is best for those who don't know much about computers or have only 1 computer or don't want to bother about all details and want it be done automatically. The download would be done automatically and SP3 would be installed.
2. Download full SP3 setup package. This is meant for IT professionals who have to update many computers at their work, or many computers of their clients. It is better for them to download once and install the setup on every computer using the files downloaded once. This can also be used to slipstream SP3 into Windows XP CD.
SP3 contains many updates that patch many vulnerabilities in Windows XP whether you are using computer at home or not. So I advise you to keep your windows up to date and install SP3.
Edited by Romeo29, 27 August 2009 - 09:43 AM.