Poll From Online Manual
A poll is used for voting. You can create whatever options (answers) you want along with the question to go along with them.
You can create a new poll (if you have the proper permissions to do so) by clicking on the New Poll button inside of a board. You can also add a poll to an existing topic by clicking on the Add Poll button on the bottom of a topic.
For more information about all of the options in a poll see Poll Options.