Here's a primer on blogging in Divi that I shared in one of the forums. I'm reposting here in case it is of use to anyone. It explains some of the main terms relating to the set up of blog posts, blog pages and blog templates in Divi.

As you may know, WordPress is centered around posts and pages. Pages are mainly for permanent site content (e.g. about pages, contact pages and so on). Posts (aka "blog posts) are more like news articles, typically being ordered / viewed based on the time they are published. The lines blur a bit, but it is the collection of posts on a site that are usually referred to as the "blog". WordPress itself lets you create, publish and edit posts. It used to give you a basic text editor for writing the content of the posts, but now it has a more advanced editor (called Gutenberg) which lets you add "blocks" to your posts. Blocks are things like text, images, videos, etc. Each of these posts can be viewed individually, but WordPress also includes a "blog page" which is a page that shows a listing of your posts, with the most recent at the top. This blog page can be displayed as the homepage, or as sub-page on the site.

Divi adds its own advanced editor for posts (and pages), called the Divi Builder. It was developed before Gutenberg and has many features not available in Gutenberg. What Gutenberg calls blocks, Divi calls modules. So you have three ways of editing the content of posts – the original WordPress editor, WordPress's Gutenberg editor with blocks, and Divi's Divi Builder editor with modules. It's a personal choice which editor you use. The original "classic" editor is the simplest while Divi is the most feature rich (but with a steeper learning curve). Gutenberg falls somewhere in the middle of the two.

Divi Builder can also be used on pages, including the WordPress "blog page". For this reason, it contains the "blog module" which essentially returns the same blog listing as the blog page. This means that a Divi Builder page with nothing but a blog module on it will function like the standard WordPress "blog page". But since the blog listing is now a module, it can be moved around the page layout, have other modules added above, below and beside it, etc. You can also use the blog module in other ways, such as for adding a "recent posts" section to a page.

Now, another (very useful) feature of Divi is the "theme builder". Basically what it does is let you create a templates for your posts / pages. The templates are actually made of three parts – a header, a body and a footer. Each is itself a Divi "layout" (i.e. a place to put and arrange modules into sections, rows and columns). Say, for example, you wanted each post to have a newsletter signup form at the end. Rather than having to add it manually to each post, or use code to insert it, you can instead create a template in the theme builder and add the Divi "email optin" module to the template. In this case, since we want the module to appear alongside the post content, we would put it in the "body layout" part for the template.

Divi gives you ability to select which pages / posts on your site you want the template to apply to. If you choose the "All Posts" option, then the template will apply, obviously, to all your posts and will thus essentially be a "blog template".

If you saved the template at this point, you'd notice that all your posts would have a newsletter signup… but no content. That's because we haven't yet told Divi where in the template to place the main blog post content. To do that we need to add a "post content' module. This is a special module that acts as a placeholder for the blog post content. With that in place, your template would now show the post content along with the newsletter signup.

I hope that clarifies the relationship between them the various components, but please ask in the comments below if anything is unclear to you.