Mcrypt is a replacement for the popular Unix crypt command. crypt was a file encryption tool that used an algorithm very close to the World War II Enigma cipher, which was broken. Mcrypt provides the same functionality but uses several modern algorithms such as AES. Libmcrypt, Mcrypt's companion, is a library of code which contains the actual encryption functions and provides an easy method for use.
I use Laravel quite a lot and it requires mcrypt. I noticed mcrypt has a lot of information in a lot of different places. I want to combine that information and maintain it so developers who use frameworks built on mcrypt have a one-stop-shop if they want to know more. I am not a mcrypt source contributor, but I encourage and BEG you to fork this and improve the docs - and one day if you dare... THE CODE!