@selee Thank you for posting your query on Microsoft Q&A and for using Azure services.
Let's break this down and try to answer question by question.
You are trying get a clear understanding on how private link and private endpoint work.
When configuring Private Endpoint, communication is possible through server direct, but communication is not possible through VIP.
Private Link service can be accessed from approved private endpoints in the same region. The private endpoint can be reached from the same virtual network, regionally peered VNets, globally peered VNets and on premises using private VPN or ExpressRoute connections.
When creating a Private Link Service, a network interface is created for the lifecycle of the resource. This interface is not manageable by the customer.
A single Private Link Service can be accessed from multiple Private Endpoints belonging to different VNets, subscriptions and/or Active Directory tenants. The connection is established through a connection workflow.
I'm not sure about the exact difference between private link and private endpoint.
Azure Private Endpoint: Azure Private Endpoint is a network interface that connects you privately and securely to a service powered by Azure Private Link. You can use Private Endpoints to connect to an Azure PaaS service that supports Private Link or to your own Private Link Service.
Azure Private Link Service: Azure Private Link service is a service created by a service provider. Currently, a Private Link service can be attached to the frontend IP configuration of a Standard Load Balancer.
Reference: Private link frequently asked questions
Additional info: The Private Link Service must be deployed in the same region as the virtual network.