- An external style sheet is a separate file where you can declare all the styles that you want to use on your website. You then link to the external style sheet from all your HTML pages. This means you only need to set the styles for each element once. -Tags are labels you use to mark up the begining and end of an element. ... The only difference between an opening tag and a closing tag is the forward slash "/". You label content by putting it between an opening tag and a closing tag. HTML is all about elements.