Nodes are essentially hierarchical entities. So we created an entity to link nodes between them no matter where/what they are. Tags are meant as tag nodes, we couldn’t be more explicit. But if you didn’t understand here is a schema:
You can see that tags can gather heterogeneous nodes coming from different types (pages and projects). Tags can be used to display a category-navigation on your theme or to simply tidy your backoffice node database.
Did you notice that
Tags are related to
Nodes entities, not
NodesSources? We thought that it would be
easier to manage that way not to forget to tag a specific node translation.
It means that you won’t be able to differentiate tag two
NodesSources, if you absolutely need to, we encourage you to create two different nodes.
In the same way as Nodes work, tags can be nested to create tag groups.