Via Reddit, we have a link to a brief history of that key next to the spacebar on Apple keyboards. It's unofficially called the Apple key, splat, the pretzel key, or the propeller, but the official name for it is the Command key. On the Apple II keyboard, the keys on either side of the spacebar were different; one was the "open Apple" and one was the "closed Apple." For some reason the open Apple key was the one that did more things, so to this day I still forget there's another key over there on the right. In fact, I called it the open Apple key for many years, and finally broke the habit about the time the Apple logo disappeared off that key entirely. Check out the story of how it came to be, and if you haven't heard it before, it's an interesting Steve Jobs tale.
Check It Out: Apple's Command Key Origin Story