Cookies are small hidden features in the game. They came about as not every feature I tried to add to TB2013 worked as intended. So rather than releasing the game with a naff feature I hid them as cookies. Cookies are somtimes called "Easter eggs" as you have to hunt them out in the same fashon as your eggs on Easter morning!
Easter egg (media) - Wikipedia, the free encyclopedia
See here for what they are and how to enable them:
Title Bout Championship Boxing - Manual