What is the WordPress approach to custom data?

Welcome!

As the comment from jdm2112 says, WordPress has the ability for you to create Custom Post Types. You can also make custom taxonomies, custom fields, and more. If you’re new to this, then I would recommend you check out Generate WP as a resource. I find it’s a great tool for getting a handle on what’s possible.

Make your CPT
There are many plugins that can help you do this, but it is very easy to create your own.

If you need to get an idea of what that looks like, head over to the WP post type generator and play around with it for a bit. Once you feel like you’ve got a handle on it, you can add it to your theme functions.php, or even better, make your own plugin (my personal recommendation).

Add Custom Fields
You can make your own meta boxes as well, but I actually recommend ACF for this. Their pricing for Pro has gone up considerably, but their product is pretty dang amazing.

I hope that helps get you started. CPT and ACF are my WP bread and butter.