Hi Claus, Generally, Template Groups” allow you to have multiple files representing different layouts or even pages within it. There are really a bunch of different ways to work with them (or not)
Let’s assume you have a “Blog” Template group
index.html - Represents the template group - so when you visit the “Blog” page, and view the article listings, that is the page that is referenced
article.html - For example COULD be another page in that group. It stands to reason that the design for a blog article would be different for the index/listing page so you can apply a different layout and create different layout sets to article.html that is specific to the post.
It can actually go deeper than that, but that would be the simplest way I can think to explain the “Why?”
Hoping that’s helpful
Field groups are there so you can create different sets of fields for different types of content. For instance a news/blog story may require different fields to say a product or a business profile.
A news/blog post might require fields for excerpt, story, related posts, main photo and so on.
A product might require fields for product photos, description, price, sale price, options (product variations such as colours) and so on.
A business profile might require fields for company name, logo, description, address + contact details, map information, link to web site and so on.
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