In HTML the body tag holds all the visible part of a webpage. So the <body> is a container tag. If we write any thing into <body> & </body>, it will visible in web browser.
Also Read: Difference between CSS initial and inherit
In HTML the <body> tag is child of <html> tag. So lets try with basic HTML templete which will clear everything if you are new in HTML.
<html>
<head>
<!-- contain title tag, style of an element
or link to external stylesheet
user can't see in browser page area
-->
<title>Hello World</title><!-- show the text in web browser title bar -->
</head>
<body>
What you have put here will display in a web browser
<script>
Javascript can be written in head tag or anywhere in body tag enclose with <script>
</script>
</body>
</html>
In html the <html>, <head> and <body> tag can be used one time. So you can’t use <body> tag multiple times.