Episerver comes with a logging API, which is an abstraction for writing log messages from the system. Logging is useful when you troubleshoot and locate application problems.
The logging API
Commerce also uses EPiServer.Logging, which is used internally by the Episerver assemblies for all logging. However, a third-party product or implementation can use the API. When you create new sites using the Episerver Visual Studio integration, the EPiServer.Logging.Log4Net package is installed by default, which is the log4net implementation of the API.