Hi there,
You don't need to use mark-up or anything like that. Power Automate makes it easy for non-developers to put in custom stuff with "Dynamic Content". "Dynamic Content" is all the stuff from your trigger (as an example) ready for you to just click.
Now, you're saying "an email" - are you referring to the "Start & Wait for an Approval"? If so, it's the same thing anyway - go, click open the email / approval (in edit mode, in power Automate), and click into the text of the email. See how this thing pops up and has "Dynamic Content" and "Expressions"? Click on Dynamic Content. If you scroll alllllllllll the way up, you're going to see all of the different Column Names from your originally triggered item. You can click on one of those, and you'll see a little teal label get put into the body of your email.
And that's it. Give it a shot, see if that's what you're looking for.
R