setinterval « global « Javascript Data Type Q&A

1. Javascript Anonymous Functions and Global Variables    stackoverflow.com

I thought I would try and be clever and create a Wait function of my own (I realise there are other ways to do this). So I wrote:

var interval_id;
var countdowntimer ...

2. JavaScript setInterval    stackoverflow.com

This is an example from a tutorial about setInterval, but it doesn`t explain it sufficiently for my newbie brain. I would appreciate if you could answer these questions i) does the 1000 ...