Unlike modern PCs and MACs, it didn't have a START menu or toolbar; it had a program manager application. It was one of the first GUI Windows platforms, an upgrade of Windows 3.0.
3.1 was the first system I ever worked with, waaay back when I was four or five. 3.1 was a good machine, capable of handling any game from Reader Rabbit to the Oregon Trail (CD).
But Windows 3.1 will be dear to me forever, for it was my first computer OS ever.