In Dot Net, Web.config and Machine.config files serve distinct purposes. Web.config is specific to each web application and resides in the application’s root directory. It contains settings that apply to that particular application only, such as connection strings, custom error pages, and security configurations. On the other hand, Machine.config is a system-level configuration file located in the .NET framework folder. It provides machine-wide settings that apply to all ASP.NET applications on the server. Changes to Machine.config affect all applications, while modifications to Web.config impact only the individual application. Understanding this contrast is crucial for managing configurations effectively in a Dot Net environment.