I’d just like to interject for a moment. What you’re referring to as the Windows key, is in fact, the command key, or as I’ve recently taken to calling it, the command button. On a keyboard made with the Microsoft Windows logo, the Windows keys are identical in function to the Mac Command keys, as is the ◆ Meta key on a Sun or another Unix-oriented keyboard. Conversely, when an Apple USB keyboard is used with other operating systems, the Command keys function as Windows keys or Meta keys.

The Windows logo key (also known as Windows key, Winkey, start key, logo key, flag key, super key, command key or flag) is a keyboard key which was originally introduced on the Microsoft Natural keyboard in 1994.

Yes, it’s equivalent to the Mac command key — it’s the Windows command key. DOS keyboards featured “Ctrl”, “Alt”, and “Cmd”. Apple, being a derivative, featured the same three keys (eventually putting the Apple logo on the Cmd key as a distinguishing feature, since Windows had no Cmd key for a long period). Windows, on the other hand, got rid of the key (technically, not entirely — the OS always supported it, but most programs didn’t bother, since keyboards typically didn’t ship with them) for a while, then re-added it to its spec, putting a Windows logo on it where Apple had put an Apple logo on their Cmd key.

The term “Windows key” is relatively common in usage, in the same way that “Apple button” is (people will say “Apple Tab” or “Shift Apple T” or whatever to describe key combinations) — they’re both referring to the same underlying keyboard function, which is “command”.