Role of Keycloak in Microservice Architecture

Hello All,
I am new to Keycloak and so far i like the way it provide out of the feature to support security in microservice architecture.

i need some architecture advice on what role Keycloak from user perspective , i know it does authentication and authorization but i want to know what part it handles about user.

say i don’t have any user in my application then registration of user and user profile management. my question is how registration flow will work , will whole user management is advised to be done by Keycloak or limited details of User like User email , name , password needs to be there in keycloak and rest can be in another service ?

Lets assume that there another service managing other details of user except mentioned above then how user records will have any ref. to each other like userid or something else and how keycloak will generate it ?

Basically i am not able to fully imaging the flow of user management in distributed/microservices application architecture

Thank you
Dheeraj Kumar