Create new topic
Voting + discussion
People will be able to cast their votes and discuss the topic.
Discussion only
People will be able to discuss the topic.
Choose this option if you want to create a place to rate (on a 1-10 scale) and discuss an item, and then add it to a ranking. It can be a person in their profession, or any thing; real or abstract. The item will have its own OpiWiki page.

More info at Guide: Items. Examples at Items database.
Choose this option if you want to directly compare two or more items or simply put some items in a competition. Users will have to choose one or more items over the other(s). The items can be two or more politicians, sportsmen, books, video games, songs, or any other.

Examples at Choices.