Taxonomy in WordPress can be used to arrange, classify and group post. WordPress has three built in taxonomies that you’ve probably used already. These are : Category, Tags and Link Category.
Understanding the custom Taxonomy in WordPress
So, by default a new custom one will have:
domain/your taxonomy name/post name
in the url.
This is the importance of Taxonomy SEO wise. Search engines will catch them rightly.
How to add custom Taxonomy in WordPress?
You can read the WordPress Codex on how to create taxonomy yourself by hard coding or you might be interested to use this plugin; which will add many more features. You can contact the Plugin developer through his blog if you face any problem.