Text Response questions are basically text fields for open ended questions. There are two types of text response questions that you can add to your survey: single-line and multiline. Using this question, you can get people to provide keyboard inputs as their responses (such as enter your name or enter your phone# or even provide your comments below).
In order to use a Text Response questions, simply drag it from the list of questions (on the left side of your survey editor screen) and drop it onto the right side of your survey editor (where you see a live preview of the questions).
Once the question has been added, you can view the question options on the left side (including the option to make the question single-line or multiline.
Watch this video tutorial on text response question types:
More on text response questions here.