Windows RT Driver
Microsoft Windows RT is the official name of the version of the Windows operating system running on the ARM processor. The driver for this operating system is the operating system built-in driver.
In-os Driver
Windows RT In-os Software is a driver that has been installed on your computer to support basic printer functionality; If most of the buttons in the printer control Panel are not available, you will not be able to use the EFax feature (if your printer has that feature) and scan output features such as scanning to e-mail.
Therefore, you do not need to download and install any other software from HP to use your printer. You can also use this software for basic printing, scanning, and faxing tasks, and for importing images from memory cards If your printer has these features.
What types of Windows 8 drivers can I use for my HP printer?
To find a Windows 8 driver that is appropriate for your HP printer, use the HP Printer Setup wizard. Not only does the Printer Setup Wizard automatically find the right driver for you, it also shows which drivers are available, allowing you to choose the software that best suits your needs.
About Third-party Web sites that provide HP printer drivers
If you use a search engine such as Google or Bing to search for Windows 8 drivers that apply to your HP printer, you may go to a non-HP website and they will also offer HP drivers or HP drivers to download "services", but usually charge. You should know that the Windows 8 printer driver for HP products is free of charge. You can download it free from the HP Customer Service center, install from the Windows 8 operating system ("in OS"), or use Windows Update to obtain it, depending on the type of driver available to your product.