From the documentation:
The program looks for a word in the rare words database and for three other words with close lexical properties. The tweet is the definition of the first word, the poll choices are made of all the words shuffled. The program then posts the poll and the tweet containing the poll, and stores the tweet’s id and the right word for the poll in a database. Next time the program is run, it will begin by tweeting the right answer for the poll in reply to the poll’s tweet.
See also: list of Twitter bots that post polls.