What is the purpose of "ASP.Net" folders?

According to the ASP.NET Web Site Layout

App_Browsers

Contains the browser settings ( .Browser files) that ASP.NET uses to identify individual browsers and determine their capabilities. For more information, see Browser Definition Schema File (Element browsers and How to: Detect browser types and browser features on ASP.NET Web pages .

App_Code

Contains source code for utility classes and business objects (for example, files .cs , .vb , and .jsl ) that you want to compile as part of your application. In a dynamically compiled ASP application. NET compiles the code in the App_Code folder in the initial request for your application. Items in this folder are recompiled when changes are detected.

  

Note: Arbitrary file types can be placed in the App_Code folder to create strong type objects. For example, placing Web service files (files .wsdl and .xsd ) in the App_Code folder creates hard proxies types.

Code in the App_Code folder is automatically referenced in your application. In addition, the App_Code folder may contain subfolders of files that need to be compiled at run time. For more information, see Code Folders Shared on Web Sites ASP.NET and codeSubDirectories element for compilation (ASP.NET Settings Schema) .

App_Data

Contains application data files including MDF files, XML files, as well as other data storage files. The App_Data folder is used by ASP.NET 2.0 to store a local database application, which can be used to maintain membership and role information. For more information, see Introduction to Association and Role Management Basics .

App_GlobalResources

Contains resources ( .resx and .resources ) files that are compiled into assemblies with global reach. Resources in the App_GlobalResources folder are strongly typed and can be accessed programmatically. For more information, see ASP.NET Web Page Features Overview.

App_LocalResources

Contains resources (files .resx and .resources ) that are associated with a particular page, user control, or master page in an application. For more information, see Overview of Web Page Features ASP.NET .

App_Themes

Contains a collection of files (files .skin and .css , as well as image files and generic resources) that define the appearance of ASP.NET Web pages and controls. For more information, see the ASP Themes and Appearances .NET .

  

Note: The content of application folders, other than the App_Themes folder, is not used in response to Web requests, but can be accessed from the application code.

App_WebReferences

Contains reference reference files ( .WSDL files), schemas ( .xsd files), and document discovery files ( .disco and .discomap files) by defining a Web reference for use in an application. For more information about how to generate code for XML Web services, see WSDL Tool (Web Services Description Language) (WSDL.exe) .

Bin

Contains compiled assemblies ( .dll files) for controls, components, or other code that you want to reference in your application. The classes represented by code in the Bin folder are automatically referenced in your application. For more information, see Code Folders Shared on Web Sites ASP.NET .