Appearance vs functionalities

And why is it important to distinguish between appearance and functionalities?

Because appearance usually depends only on your theme or how pages are built, they can interact with your plugins or other parts of your website, such as the Post types.

On the other hand, functionalities heavily depend on one or several factors. So, adding new functionalities should be planned more carefully because it may create an unwanted chain of dependencies that will make your website harder and harder to be managed in the future.

Imagine that you have installed an e-commerce plugin that is not well known and doesn’t have a good support system. This will lead to problems because it will take a lot of work to find plugins that interact with it.

You can think of appearance as “which and how information is presented to the user.” And functionality as “what the user can do”.