It is based on a word list originally posted to the Usenet group sci.crypt by Peter Kwangjun Suk. The list contains 7776 short English words, abbreviations and easy to remember character strings. See above paper for an explanation and analysis. Truly random quantities are a raw ingredient for many cryptographic applications. Generating randomness by computer can be done but offers numerous opportunities for error and attack.
Simple dice present an attractive alternative if used properly.
This paper presents a number of techniques for using dice in conjunction with modern cryptographic software. A word list for generating passphrases using dice is presented in a companion document. A simple Java applet to help you generate random passwords for login control and other purposes. Uses the time between your key strokes as a source of randomness. Not as secure as the diceware method, above.