1.) It allows you to log information as part of the JavaScript development process. Allows you to interact with a web page via JavaScript expressions.
2.) Go to top right of screen and click on the three vertical dots, go to More Tools, then Developer Tools. You can also use Ctrl+Shift+J on Windows.
3.) Creates a message inside the console, instead of creating a pop-up message that has to be clicked out of every time.
4.) By typing the changes you want to make into the console as though you were writing a JavaScript page. Changes will be saved if you save the page, but refreshing will clear the changes.