Polls can be posted either on the front and section index pages as a site-wide, independant poll, or attached to a story as a story-specific poll by the story author. Independant polls have their own comments associated with them, with all of the comment features present in stories, while story-specific polls share comments with the story; that is, whether you're viewing the story or the poll results, you see the same comments.
To post site-wide polls, you must have the perm edit_polls (A.12.15). This perm also gives you the ability to edit existing polls, including polls attached to stories. To post polls attached to stories, you must have the perm attach_poll (A.12.3) and story_post (A.12.35).
All polls can handle any number of possible answers up to the maximum number of answer fields displayed on the form, which is set with the variable poll_num_ans. If poll_num_ans is reduced, existing polls with more than the new number of answers are not affected.
If the variable allow_ballot_stuffing is on, users with the perm edit_polls can change the number of answers to each possible result at will. This does not affect tracking who has voted in which poll, and if you zero the poll people who have already voted will not be able to vote again.
For information on comments attached to polls, see section 4.6.3.