What does GP call the 'template' it uses to display post content?

I have someone helping me set up some custom post templates in GP.
She said she needs to figure out "what GP calls the template it uses to display content."

She did this with the Kadence theme and found it challenging because Kadence has a string of separate templates that go into creating a post.
She said it was a bit of a puzzle to figure out, so I'd like to help her if you good folks can tell me. She believes that GP will be similar and
than she can trace the theme... "knock on wood" - her words.

She has the template code, she will be creating a child theme along with figuring out the 'template' used to display post content.