Here's an original Mac keyboard:
http://upload.wikimedia.org/wikipedia/commons/7/76/Apple_Mac...
It's remarkably simple compared to a modern one, Mac or PC. I believe the smaller key next to the Command key is Option. I think Option would have served as a way to access more obscure keyboard shortcuts and to enter "special" characters, as it is today, although I could easily be wrong going that far back. Note the total lack of a Control key, though, as well as fairly basic amenities like arrow keys.
By the time of the Mac Plus, there was a numeric keypad and arrow keys, but still no Control:
http://en.wikipedia.org/wiki/File:Apple_Macintosh_Plus_Exten...
The Control key showed up with Apple Desktop Bus keyboards:
http://en.wikipedia.org/wiki/File:Apple_ADB_Keyboard.jpg
Note the "proper" placement of Control and Caps Lock, unlike the universal wrongness we see today. I honestly do not know what purpose it served at the time. The main use of Control on the Mac, activating contextual menus in the absence of a right mouse button, didn't show up until about a decade later. My recollection from this period was that Control was very rarely used other than for things like talking to other systems that cared about those sorts of things through terminal emulators.