What is a host in .NET Core and how does it relate to an application?

In .NET Core, a host is responsible for managing an application's lifecycle and providing services such as dependency injection, configuration, and logging. The host is responsible for setting up and running the application, and it manages the application's resources such as threads, memory, and I/O.

There are two types of hosts in .NET Core: the generic host and the web host. The generic host is used for console applications and services, while the web host is used for web applications.

The generic host provides a set of built-in services, such as configuration, logging, and dependency injection, that can be used to configure and run the application. The web host builds on top of the generic host and provides additional services for web applications, such as HTTP request processing and routing.

The host is typically created in the application's entry point, such as the Program.cs file in a .NET Core console application. The host can be configured using a builder pattern, where services and middleware are added to the host using extension methods. Once the host is configured, it can be started by calling the Run() method on the host. The host will then run the application until it is stopped or terminated.