What is Template in WordPress? How to use Templates in WordPress

A Beginner’s Guide to WordPress Page Templates
Enter page templates — a way to get more control over your site’s look. In some ways, page templates are very similar to themes. Both are files with code that tell your site how to display information. As the name suggests, however, a page template only controls the style of a particular page (or type of page). Many themes come with various page templates to choose from, but you can also create your own. That way, you can decide exactly how it should be set up and what pages should be assigned to follow that template.
How to Use WordPress Templates
The Main Index template drags your blog posts out of the MySQL database and inserts them into your blog. The filename of the Main Index template is index.php. The first template tag in the Main Index template calls in the Header template, meaning that it pulls the information from the Header template into the Main Index template.
WordPress.org
When someone visits a page on your website, WordPress loads a template based on the request. The type of content that is displayed in by the template file is determined by the Post Type associated with the template file.  The Template Hierarchy describes which template file WordPress will load based on the type of request and whether the template exists in the theme. The server then parses the PHP in the template and returns HTML to the visitor.
WordPress.org
What you are seeing is by deafault, WordPress does not allow editing of the page set as the Blog page – you would get a message like so “You are currently editing the page that shows your latest posts.” and the edit content box would not show up unles you already had content in it when you initally created it.
How to Create a WordPress Page Template
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Creating Blog Templates in WordPress
In this next step, we’re going to tell WordPress which page it should use for our blog homepage. Basically, this is sort of a phantom page that we need to point to that will use our home.php template file we just created. To do this, we can either go into the “Settings > Reading” area in the admin and choose our page under the “Front Page Displays” area or we can use the WordPress Customizer. If you decide to use the customizer, navigate to the “Appearance > Customize > Static Front Page” section and click around a bit. You’ll see exactly what to do. Personally, I’d get used to using the customizer if I were you, because that seems to be where WordPress is heading for many of these types of settings.
How to Create a Template for A Single Post In WordPress
Template for Custom Post Types is essentially the same kind of plugin we used in this tutorial. It adds the drop down box when creating a post allowing users to choose a template. However, it also requires files to be created and saved in the theme’s folder. One of the highlights to this plugin is that you can select custom templates for posts, pages and other content in WordPress. If you’re averse to using a four-year old plugin, this one is more current.
WordPress Themes and Templates Explained
I am looking at purchasing a third party theme/template to build my webiste. The author states that it is a Photography WP Theme https://themeforest.net/item/diamond-photography-wordpress-theme/9274644?ref=cirvitis, but he also has a photography website template https://themeforest.net/item/diamond-photography-website-template/9718334?s_rank=17. I am wanting to build my site on WP.org – which is the best to purchase?