Answer 1

Console. log is used to see the output in a console. To see the output of your code you can go to : Developers Tool in Firefox or Chrome.
Where do I use it? When I write code , and want to try it out instead of having a popping up alert window all the time I just ue console.log.

var name = prompt("What is your name?" )
alert (name);
OR
console.log(name);