Checkbox makes it possible to give multiple answers to a questions without allowing free text answers. To add a question to your Signup form with multiple options, follow these steps:
Add a question to your Signup form
Click on `Pages` in the menu
Click on `Forms`
Click on your form under Signup form
Click on `Add field`
Enable multiple options
Under Type, choose Checkbox in the drop down menu
Under Values, type in the different options (comma separated as in the example)
Under Type you can also choose Multiple choice. Multiple choice lets you pick one of several visible options. With Checkbox you can select more than one alternative.