The Most Preferred Matrix question type asks the respondent to choose one of two options per row. You can add as many rows as you like, presenting the respondent with a number of either/or choices.
Using the Most Preferred Matrix question type is pretty straightforward. If you need your respondent to choose their favorite of two choices, this is the question type for you.
[edit] Example
When selecting a question or content type, you can see what you're getting before you make your decision! Click on the Examples link at the top-right of each question type box. You'll get a brief preview of what the type looks like and how you might use it.