Here I have a basic example of a select tag for starters. So the basic idea here is to have a single select element, and then a nested option element for each option in the selection element. By default the inner text of the option element will be the value property of the select element. So when I set an on change event listener to the selection element the value of the selection element will change each time the user selects one of the options in the select element drop down menu.
So by default the value of the select tag will be the inner text of the current option element that is selected. However the value property can be used to set that to something else, and then the inner text can eb used for a display name, and the value can be used as some kind of id for the selection option.
The disabled property of an select element can be used to disable a selection element, or any option in a selection tag if it is not currently applicable. For example say you are making some kind of simple game demo that contains a display object that can be controlled by an AI script, or user input. A select tag can be used to switch between the two, and depending on the current value of the first select tag another select tag can be enabled or disabled.
So then the disable attribute will come into pay when working out some kind of user interface that is a little involved. Where there are whole menus that will end up being disabled depending on other settings, or the state of the application.
So select tags in combination with option tags are the standard html way of creating an interface where a user can select from two or more options. it is often used with additional events such as the on change event to define what happens when the state of the select tag changes.