In ASP.NET Core, Request delegates are used to build the request pipeline i.e. request delegates are used to handle each incoming HTTP request. In ASP.NET Core, you can configure the request delegates using the Run, Map, and use extension methods. You can specify a request delegate using an in-line anonymous method (called in-line middleware) or You can specify the request delegates using a reusable class. These reusable classes and in-line anonymous methods are called middleware or middleware components. Each middleware component in the request processing pipeline is responsible for invoking the next component in the pipeline or short-circuiting the pipeline by not calling the next middleware component.