- used to stylize a very small part of text by CSS(Cascading Style Sheets).
   
 - groups content, used mainly to add a class to a groups of different tags and apply CSS.
   
 - groups related content, helps the  disabled people to communicate to the computer through the assistive technology , forexample: for the screen readers.etc
   
 - groups independent, self-contained content, helps the  disabled people to communicate to the computer through the assistive technology , forexample: for the screen readers.etc