Often times, its helpful to make a seperate style sheet to declare the classes and ID's to help make the programming sheet a bit nicer. This is often referred to as CSS or
Cascading Style Sheets.
CSS is a language for laying out and structuring web pages.
Rel - stands for Relationship
The link to the seperate style sheet is linked in the head section of the document. The link is declared like this:
< link rel = "StyleSheet" href="" > - the path to the stylesheet is provided in the quotations after "href". The style sheet, as mentioned before, contains all the tags and classes and is saved as a .css file.