* Startup.cs : [Startup Class](xref:fundamentals/startup) - class configures the request pipeline that handles all requests made to the application.
* Program.cs : [Program Class](xref:fundamentals/index) that contains the Main entry point of the application.
* firstapp.csproj : [Project file](/dotnet/articles/core/preview3/tools/csproj) MSBuild Project file format for ASP.NET Core applications. Contains Project to Project references, NuGet References and other project related items.