Windows 7 is an operating system from Microsoft released in 2009. It is superceded by the release of Windows 8 in October 2012, but Microsoft will continue to provide mainstream support for the product until 2015 and extended support through to January 2020.
Techopedia explains Windows 7
Windows 7 followed Windows Vista and featured various changes from prior operating systems. One of these was the Quick Launch Toolbar, which revolutionized how the users find various commands and menu options. Windows 7 also includes items like support for virtual hard disks, gaming additions, and other new features. As for machine requirements, Windows 7 requires a 32-bit or 64-bit processor with at least 1 Ghz in order to run, as well as 1 GB of RAM for a 32-bit system, and 2 GB for a 64-bit system. The machine must also have 16 GB of hard drive space.