The alert is just a keyword that the browser recognizes and knows what it should do. It gets the browser to do something.
So,it has to be something that the browser knows about.
This is also known as a function because it's a little bit of functionality.
This is actually a little bit of behavior which we got by writing JS code.
The middle part here in green is the message.
This is what we want to show up in the pop up and you can change that message to anything you wish.
Inside a quote, we're telling the computer that this is not code, this is just text, so that it doesn't treat it as a keyword like alert.
Finally at the end, there is semi-colon(;) and that denotes the end of this sentence or the end of your instruction, so that the browser doesn't get confused between one line and the next line doesn't combine it into a single line of instruction.
