It depends on what you are changing or adding.
You can add content – and styles in the content section of your templates – including text and images. You may need to know some HTML and CSS to do more complicated layouts/styling of the content you are adding.
But to change the layout of the underlying template, you would need to create a custom template or modify an existing one (always best done in a Child Theme).
A more specific example, including a page link, might better answer your question.
What I basically want to do is make it so that a third party can add information to various parts of the page using the same text field
Not sure how useful a link would be here, I’m not actually having an issue with my website, I just want to be able to do something like this:
HEADING
Paragraph 1
*Videos and widgets*
SUBHEADING
Paragraph 2
But I’m curious to know if there’s a way to do that without adding the paragraphs into the template for my page, so that a third party can change it to whatever they want without possibly damaging the site
In case anyone facing the same issue finds this, I ended up putting the paragraphs in div tags and styling them appropriately
Kind of pseudo-resolved