appsettings.Development.json is a configuration file used in ASP.NET Core applications for storing configuration settings specific to the development environment.
In an ASP.NET Core application, the appsettings.json file stores configuration settings that are used across all environments. However, sometimes you may want to have different configuration settings for different environments, such as development, production, or staging. This is where appsettings.Development.json comes in.
When you run an ASP.NET Core application in the development environment, the configuration settings in appsettings.Development.json are applied in addition to the settings in appsettings.json. This allows you to have different configuration settings for different environments without having to modify the settings in appsettings.json.
For example, you might want to have different database connection strings or logging settings for your development environment. You can specify these settings in appsettings.Development.json, and they will be used only when the application is running in the development environment.
Note that appsettings.Development.json is just one of the possible environment-specific configuration files. You can create similar files for other environments, such as appsettings.Production.json or appsettings.Staging.json, and the settings in these files will be applied when the application is running in those environments.