What is it called when you want the audience to decide between two options

Voting, Polls etc. The most common question type is Multiple Choice, in which participants can choose between several options that you provide. You probably already know much about this type of question, since it has been widely used for surveys.
Multiple Choice is suitable when you already know what options you want the participants to vote on, i.e. you want your audience to choose only from a few pre-defined options.