We can find the web.config file in every application for web based..Here we can configure the information for the specific web application..like Authenication, modes,Compilers,Themes profile,connection string,assemblies......

web config file is a Xml based,Non compiled & Case sensitive file used for maikng connection with database.

used mainly for project configuration eg.security setting & session setting

one more thing web config file is secure (we can't display web config file in browser).

Webconfiguration file is XML file with the help of this file we manage the web application setings to run web application this file must be on web application.

The file is an XML document that defines settings & configuration  for an ASP.NET Web Application.