This indicates an OEM (Original Equipment Manufacturer) license. "OA" means the product key is tied to the hardware by the manufacturer (HP) and is intended to be activated online.

You won't find Windows Media Center, XP Mode, or the ability to join a Domain. Why Does the "LATAM" Tag Matter?

While it sounds like a mouthful of technical jargon, each part of that name tells you something important about your software and your licensing rights. Here is everything you need to know about this specific version of Windows. Breaking Down the Name