The Paragraph is denoted by the <p> and it is block level elements it's mean it's width 100% by default and that's why browsers automatically add some white space (a margin) before and after a paragraph. Each paragraph of text in HTML document should go in between an opening <p> and a closing </p> tag.
Example :
<!DOCTYPE html>
<html>
<head>
<title>Paragraph Example in HTML</title>
</head>
<body>
<p>Here is a first paragraph.</p>
<p>Here is a another paragraph.</p>
<p>Here is the third paragraph</p>
</body>
</html>if you add the extra space and extra line inside the paragraph tag then browser automatically remove the extra line and extra space and counts number of spaces and lines as a single one.
Example :
<p>
This paragraph
contains a lot of lines
as you seen in this code
but the browser
removes it.
</p>
<p>
This paragraph
contains a lot of white spaces
as you seen in this code,
but the browser
removes it.
</p><br> tag is used to create a new line without starting a new paragraph.
Example :
<!DOCTYPE html>
<html>
<head>
<title>Example of HTML Line Breaks</title>
</head>
<body>
<h2> How to use line break with pragraph tag</h2>
<p>
This is first line<br>
This is second line<br>
This is third line<br>
This is fourth line
</p>
</body>
</html><hr> tag is used to create a horizontal line between two statements or two paragraphs.
Example :
<!DOCTYPE html>
<html>
<head>
<title>Example of HTML Horizontal Rules</title>
</head>
<body>
<h2> How to use HTML Horizontal Rules inside the paragraph tag.</h2>
<p> First Line Before Horizontal Line</p>
<hr>
<p>Second Line After The Horizontal Line </p>
</body>
</html>