You probably know how to organise your content with categories. But what if you want to be able to show content from multiple categories, based on something they have in common? That’s where tags can be useful. And the good part is: you can use this right out of the box, because it comes with the Joomla core.
Read more https://magazine.joomla.org/all-issues/march-2023/joomla-explore-the-core-using-tags