HTML
HTML (HyperText Markup Language) is the standard markup language that is designed to display content in web browsers. HTML is the structure or base of a website where the content is located. HTML is used allongside CSS and JavaScript.
HTML on it's own doesn't have much detail, which is why it is used alongside CSS (Cascading Style Sheets). CSS is used to style the HTML code and make it look nice.
CSS
CSS (Cascading Style Sheets) is what tells the browser how to style the content provided in the HTML Code. CSS is responsible for positioning, coloring, and modifying the content so that it looks visually pleasing.
Some basic functions of CSS include changing the font, modifying images, and changing the background