Not sure what template you’re in? Use the WordPress body classes.

Let’s talk about WordPress body classes! But first, an explanation of what this is. This is the first short post, from what I hope will end up being several short posts, called “Quick Tips”. It can take me weeks to write a “normal” sized post on RachieVee, and so, in an effort to keep myself active in 2019, and still pass on tidbits of knowledge, I’ve started this new category. I have also categorized these “Quick Tip” posts based on developer experience. This first post is geared towards “Beginners”. This level is meant for developers just getting to know how WordPress themes work. What are WordPress body classes?
Back on topic! WordPress body classes are exactly what they sound like. They are HTML classes applied to the body tag of a WordPress site. WordPress themes use the body_class() function to apply these classes auto-magically.
If you’ve ever had an error show up on the front-end of your site, or if you’re looking to change something in a WordPress theme – taking a glance at these classes are a quick way to orient yourself. While these classes won’t tell you exactly what template to look for
Source: https://managewp.org/articles/18317/not-sure-what-template-you-re-in-use-the-wordpress-body-classes

source https://williechiu40.wordpress.com/2019/01/21/not-sure-what-template-youre-in-use-the-wordpress-body-classes/