Microsoft updating software
After an administrator approves and prioritizes these updates, WSUS automatically makes them available to any computer running Windows Update (or the Automatic Updates client on earlier versions of Windows).
Windows Update (when properly configured) then checks the WSUS server and automatically downloads and installs updates as configured by the administrators.
Ideally, you would install all current updates immediately when you deploy new computers.
After deployment, you can manually install updates, but you’ll be much more efficient if you choose an automatic deployment technique.
Because security threats are constantly evolving, Microsoft must regularly release updates to Windows Vista.