What ASP.NET Middleware can do?

Pretty much everything. Default ASP.NET Core request handling pipeline is consisting of bunch of middlewares:

• Authentication
• Authorization
• CORS
• HTTP Logging
• MVC
• Static Files
• other

Whole list of built-in middlewares can be found here:

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/middleware/?view=aspnetcore-7.0#built-in-middleware

There is possibility to write custom middleware too.