What is the purpose of the Web.config file in an ASP.NET application?

The `Web.config` file in an ASP.NET application serves as the primary configuration file for the web application. It is used to define and manage various settings and configurations such as security, application behavior, session state, connection strings, error handling, and custom application settings. The `Web.config` file allows developers to control application settings and behaviors in a centralized manner, enabling easier management and customization without modifying the codebase. It also supports configuration sections and hierarchical configuration, allowing settings to be inherited and overridden at different levels within the application.