HTML stands for Hypertext Markup Language. it is a front-end technology for servers and web browsers. it uses plain english, and is quite simple. The code is arranged into tags, one open and one closed. 

CSS stands for Cascading Style Sheets. It is another language used to design the front-end of a website server. CSS decides what you see on the webpage, and can be used to design colors, animations, and other neat things. CSS can also make websites responsive, which means that the website will change depending on the screen size and resolution.