What is a user store ? Identity data store or directory

About

A identity data store for Identity and Authentication data is where a list of identity and their respective authentication material is stored.

It's also known also as:

• a directory
• or user store.

Example and List

• a SQL database,
• LDAP server (Oracle Internet Directory, Oracle Virtual Directory, Microsoft Active Directory, …)
• An administrator distributing private keys
• A user store from a a auth provider
• a file with a list of usernames and passwords
• …