When Windows 95 arrived on the scene, Microsoft convinced keyboard manufacturers to add several new keys especially for Windows users. One was the Windows (or “Win”) key, which has a picture of a wavy flag on it.
Another was this ’Menu and Mouse Pointer’ key, which tend to get ignored.This is known as the Menu key, and it’s an alternative to right-clicking something. If you find it difficult to right-click, you can do a normal click instead (using the left mouse button) and then press the Menu key. This displays the context menu you’d normally see if you right-clicked.
The whole idea of right-clicking was brand new in Windows 95. Previously, the right mouse-button did nothing at all. As a result, there were mice around that only had one button, because that was all they really needed. This Menu key allowed users with one-button mice to get at all the right-click options their mouse was denying them.