From my understanding, a "forward telnet" session is started by a remote user who wants to remotely control a router or switch, and a "reverse telnet" session is started when the host device itself initates the telnet sessions.
What i am finding difficult to digest is why has cisco named the telnet from the device to another device as "reverse" telnet?? Any help on this answer is highly appreciated. Thanks!
Although i somehow agree with Scott, but i can find it also not that bad, plus i don't think that the name was introduced by Cisco, look it in this way:
forward telnet -> when telneting to a Cisco router from another device - Since this is the normal scenario of telneting, where you need to gain access to a Cisco router.
reverse telnet -> when telneting from a Cisco router to another device (which is the reverse of the other scenario).