How to create categories and associate them with posts

Hi guys, I'm using the Codeigniter framework, I'm fine. However, I would need help with the creation of categories associated with any hypothetical post. I'm creating a small script where every post has to be associated with a category, but it is not practical to follow the right practices for creating tables in databases.

If anyone can help me, I would be grateful.

In the database I guess I can create these tables and fields:

Post: id, title, description, category
Categories: id, category_name

So, I create categories within "Categories".
Subsequently, each post has the classic id, title, description, and assigned category.

In my home, I show all the results.
While in the category page I get only the results associated with the category.

This is how I think it should be done in words, if anyone can advise me on an article maybe it would be better. Thanks to anyone who will help me!