It'll install and/or update all required drivers, depending on your hardware. If the drivers already installed are outdated it may update them.
You can also download the latest catalyst suite (9.11) or its individual components from AMD's website:
http://game.amd.com/us-en/drivers_catalyst.aspx
Click on "Motherboard/Integrated Video Drivers" to expand it and select what drivers you want and for what OS from the menu.