What would be this website without the html ?!, nothing so thank him very much (i'm actually doing it)
The classic scheme of a html page is :
rel="icon" means that the picture in question is an icon ; type="image/png" defines the object as an image in png format ; href="favicon.png" is simply the address of the image.
To make download the user you have to make a link with the tage tag "a" from the file