Both are real services.
Windows Services have existed for over 20 years. They start most often at system startup and run permanently.
A Worker Service is also a real process, but is intended as a background service for a front-end application; it starts with the application and stops with the application.
That said, a Worker Service can also be configured to run as a Windows Service.
So from a C# perspective, a worker service is the same idea as a Task or a Thread. But it runs in its own address and memory space. Therefore, it won’t crash just because the application crashes.