Answer:
HypeTextMarkupLanguage aka HTML is a Markup Language (as in the name) and is used for making websites and functions that you would add variables using Javascript. CSS aka Cascading Style Sheets, is a style sheet. The purpose of CSS is to make the site/game or whatever your making too look nice.
Example:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Example</title>
<!-- Add Style Sheets Below -->
<style>
body {
background-color: yellow;
}
</style>
</head>
<body>
<!-- In HTML you can make buttons or links -->
<center>
<button>You can add style using CSS</button>
</center>
<!-- You can add Javascript to the button to make it play a sound or open a new window -->
</body>
</html>
