OS CPE shows common platform enumeration (CPE) of the OS. CPE is a standardized way to name software apps, OSes, and hardware platforms. CPE typically contains seven fields:

cpe:/<part>:<vendor>:<product>:<version>:<update>:<edition>:<language>

Some fields, however, can be left blank or even left off. If you take a look at the preceding screenshot, you can see there are five fields listed, one of which is left blank.

You may be wondering what does the o stands for in the cpe:/o: field in the beginning.

To clarify O stands for operating systems, A for applications, and H for hardware platforms. If you take a look at the picture, it lists four possible OSes. It's clear that the target is running Windows 7 Professional operating system, which turns out to be correct. Moving on!