Dice Pass generates random passphrases based on the Diceware system. The official way to generate a phrase is to roll 5 dice for each word you want in your passphrase and then consult the words table to find the matching word.
The resulting phrase uses real words or common abbreviations, so it is easier to remember than a random collection of characters. At the same time, the random selection of words makes the generated passphrase much more secure as it avoids the human tendency to pick words with personal meaning.
Dice Pass allows you to select the number of words in your passphrase, re-generate the entire passphrase any time, re-roll a single word in your passphrase or set the dice rolls manually for maximum security and randomness.