Where can I find the implementation of Selenium Interfaces?

Maybe a dumb question, but where can I find the implementation of Selenium Interfaces. For example, WebElement is an interface that has a click() method amongst others. Where can I find how Selenium has implemented this click()? There should be an implementation of this interface somewhere. I can't seem to find it.

Another example, Alert. We conveniently switch to an Alert and getText() or dismiss(). But where can I find exactly what selenium is doing under the hood with these functions.

Thanks much!