Answer 1

In my own words:
I would say that graceful degradation method used by web developers
to handle the a specific situation.

And the situation is: they want to use a
JavaScript or CSS features that is not supported by all browsers.

One of the ways they can handle that situation is by using graceful degradation:
They use that feature in the browsers that support it and in those that do not support it
they try to make the site degradate gracefully, meaning, in a way that will not affect the user experience
too much.