This session allows you to recap a basic web page that included some CSS. (you should have some knowledge of this from KS3)
HTML stands for Hypertext markup language and is the backbone of webpages and read by many web browsers HTML is made up of TAGS that are identified as <opening tags> and </closing tags>.
CSS stands for Cascading Style Sheets and basically is how web pages are made to look more appealing.
Internal CSS
Looking at the above code this uses internal CSS that specifies a style for a single HTML page. It is defined in the <head> element of an HTML page, inside of a <style> tag