Web Configuration File

• Configuration file is used to manage various settings that define a website. The settings are stored in XML files that are separate from your application code.
• Generally a website contains a single Web.config file stored inside the application root directory. However there can be many configuration files that manage settings at various levels within an application.
• Configuration files help you to manage the many settings related to your website. 

Some of the most frequently used configurations, stored conveniently inside Web.config file are:

• Database connections
• Caching settings
• Session States
• Error Handling
• Security

Different types of Configuration files

Machine.config: Server or machine-wide configuration file

Web.config: Application configuration files which deal with a single application

Configuration file looks like this:

 <connectionStrings>
    <add name="conn" connectionString="Data Source= UTPAL;Initial Catalog=threetier_db;Integrated Security=True" providerName="System.Data.SqlClient"/>
  </connectionStrings>