what is the Benefit of 'Log4net' namespace

Log4net is a class library which is used for managing the log in your application. it comes with very good features. have a look of the links

http://www.codeproject.com/Articles/8245/A-Brief-Introduction-to-the-log-net-logging-librar

Please don't call it a "namespace", you should refer to it as a class library, a tool, a component or something like that.

Log4net is a .NET adaptation of original Java implementation of an application error logging component from Apache. See details here....

http://logging.apache.org/log4j/2.x/index.html

So basically, it's a class library with highly configurable application error logging component. It is only when use something like this, you realize how much more it could be to a simple thing like an application error log.