Hey there, @vytaulla51! Thanks for contacting us. I’m happy to help you.
The difference between templates and pages is that when you go to Pages and choose a page to edit, you will be changing the content of the page. The actual text, images, etc on that specific page. When you edit a template you will be editing the layout of every page that uses that template. So if you add an image there, the image will show on every page with that template, for example. There are also templates for posts, not only pages.
So for general pages, you should always edit the content of it on the Page and the overall layout on the template.
The thing with the cart and checkout pages is that you don’t usually have more than one of those, so the content ends up being on the template too.
I would suggest keep editing the cart and checkout pages, instead of the templates. It keeps things consistent, and if someday you end up switching to a non-FSE theme, the page will still look as it should 🙂
I hope this was clarifying. Please let us know if there’s anything else we can do to help or if you have any questions.
Have a wonderful day!