What is HTML?
Rundown:
The easy answer is that html is the language of web pages.

In Depth:
HTML (Hypertext Markup Language) is a programming language used
on the WWW (World Wide Web) in order to create web pages.
Web browsers than interpret the HTML and display it so that users
are able to view it. HTML is actually a very simple language once the
basic concepts are understood. Just remember HTML is a client-side
language which means the data is interpreted locally
on your computer, not from the server.



What is CSS?
Rundown:
They define how to display HTML elements.

In Depth:
CSS (Cascading Style Sheets) define how to display HTML elements.
They are normally stored in Style Sheets (.css), they were added
to HTML 4.0 to solve a problem. CSS is a breakthrough in Web
design because it allows developers to control the
style and layout of multiple Web pages all at once!