Definition - What does Windows 3.x mean?
Windows 3.x refers to the third version of Microsoft Windows. It was not actually a full-blown operating system but was a 16-bit GUI program that ran on top of MS-DOS. Windows 3.x quickly became the first-ever widely accepted version of Windows. It consisted of two versions: Windows 3.0 and Windows 3.1x.
Techopedia explains Windows 3.x
Windows 3.x was the predecessor of Windows 2.x; unlike MS-DOS, it had multitasking (non-preemptive) capabilities, which means that it could run multiple programs concurrently, as well as run more than one instance of the same program simultaneously. Windows 3.0 was launched in 1990; it was then followed by Windows 3.1, Windows 3.11 (Windows for Workgroups) and Windows 3.2 (basically the Chinese version of 3.1), which were released between 1992 and 1995. Windows 3.x included a variety of programs including File Manager, Notepad, Paintbrush, Solitaire, etc. Windows Media Player was first introduced in Windows 3.0 with Multimedia Extensions, which was released in 1991.