To understand all these better we need to know some terminologies first.
They are the entities that manage and store user credentials.
The service that request and receive data from the Identity Providers.
This could be a collection of apps that we use everyday at work or could also be a website.
These are the digitally signed XML documents that encapsulate user identity data. User identity data is usually represented in the form of attributes such as email address, name, phone etc.