Confusion on service endpoint and private endpoint.

After reading the introduction of service endpoint and private endpoint, I’m still confused why we need the endpoints. So by default the PaaS services don’t have any IP address and can only be accessed via Azure portal? What’s the difference between the IP obtained via endpoints and the IP without endpoints? Let’s say in a Storage Account scenario.

I also saw someone mentioned the private endpoint is like a special NIC. If so why don’t we call the endpoints NIC or something NIC? Is it essentially an NIC or not? Thanks!