How to get drop down to change form format

I'm super new to Adobe so I'm not even sure if I'm asking my question well/correctly.

That being said I have a form that I'm working on for a project that my boss would like to be EXTREMELY user friendly. To the point of when you use a drop down box to select the type of form, it alters what you need to fill out (just by adding an extra text box). How do I do this as simply as possible?