HTML related query

what will be the difference in the output, if we put a content within ‘paragraph’ tags, written within ‘body’ tags, instead of writing the content simply in ‘paragraph’ tags, without written in ‘body’ tags?

HEAD and BODY tags are optional, in some cases, namely for things like interstitials (modals) or pop-up windows where we only need,

<p> ... </p>

A page facing the web, though, should be valid and well formed, meaning it will have a HEAD (and TITLE) and a BODY, within the root HTML element.