You can read about them here (you'll have to scroll down a bit)
http://www.cplusplus.com/doc/tutorial/control/
And here's a specific article all about range-based loops (I can't vouch for it because I only took a quick glance over it, but it seems pretty informative).
http://en.cppreference.com/w/cpp/language/range-for
(That's amazing. and Haha, nice one! I just picked it because it was easy to remember, and to my surprise, it's typically not taken ((and if it is, I just alternate to cactus3, which isn't ever taken)).)