HTML Scripts gives us way to embed or include client side script into the HTML Document. HTML script (<script>…</script>) tag is used to include a block of client side script or to call it from external source.
Internal Script-
You can define your custom block or function of client side scripting language inside a HTML Document itself.
Example:
<script type="text/javascript">
document.write("Hello Javascript!")
</script>
External Script-
If you have ready to use client side script library or custom script that you want to reuse then you can call into the HTML Document.
Example:
<script src="custom.js" type="text/javascript" />