This key is labelled “Alt Gr” and is situated immediately to the right of the space-bar on both of my Toshiba Laptops.I do not know if there is an equivalent key on conventional keyboards. Any one out there know?
On the Mac (at least in Classic) you can get all kinds of funky characters by holding down option, shift+option, or control. Not all fonts have these other characters but the ones from Apple do.