I have a question about Drop-down list boxes. Why do they get connected to work records?

I have a question about defining a drop-down list box.  I am modifying a custom page that currently has a push button that has a dynamic text on it. If you click "Clear," the button shows "Un-clear" instead. I have a request to add a second button to provide a third option. 

This cries out to be a drop-down list box instead. The values connected to the buttons are XLAT values. Currently the button is tied to a field in a work record.  I spent several hours yesterday on Google searches to find wisdom on creating a drop-down list box and then knowing what value was selected/appears visible.  I did not find what I was looking for, and therefore I have questions please.