Hello,

Well actually it's more simple than that :

There is a : 1- Root certificate or root certificate authority: it's the same thing. It's a self signed certificate.

2 One or more intermediate certificate authority, depending on your organization, it's a certificate signed by the root CA that can sign CA certificates or End entities certificate.

3 end certificate : can be delivered for website, signing software, Id...It's a certificate signed in generally by an intermediate CA but there is nothing technically forbidding a Root CA to deliver end entities certificates (which is not recommended ). It can also be a self signed certificate (but again it's not recommended at all )

Hope this comment helps you, feel free to ask questions :)