The Placeholder Text field setting adds grey example text to your field that disappears when people start typing, and isn't recorded in your results.
If you want to set a default answer that will be recorded in the entry if the person filling out your form doesn't change it, use the Predefined Value field setting instead. If you have both settings filled out, Predefined Value will show instead of Placeholder Text.
To add placeholder text to a field:
You can add placeholder text to the following field types: