The HTML <style> tag is for declaring style sheets within the head of the HTML document and the technique is known as Internal CSS to add CSS to HTML Page. CSS can be used in various ways in HTML. One of them is by using Internal CSS i.e. using a <style> tag.
The <style> tag is used in the <head>…</head> tag. It defines CSS style for a single page.
Example
You can try to run the following code to use the <style> tag
<!DOCTYPE html>
<html>
<head>
<style>
h1 {color: green;}
p {font-size: 14px;}
</style>
</head>
<body>
<h1>Tutorials</h1>
<p>We provide free learning content.</p>
</body>
</html>