Explanation: This menu shows the current firmware version of your camera.
Firmware is the internal camera software, responsible for all the functionalities, menus etc. From time to time manufacturers publish updates to the firmware when a camera is already sold to introduce small new features or to correct errors.
At the time of writing (January 2013) the current versions of the D7000 are A 1.02 and B 1.03, they contain only corrections of small errors compared to the earlier versions.
Tips: Update your firmware only when you know what the update does and if the improvements are beneficial for you.
The Nikon website is the best source to get updates, there you will also find instructions for installation.