You see if people using logging frameworks would have look for real at Beacon or systemLogger and add one single appenders and publish the code then we would have more of them. We will merge Beacon and SystemLogger with Doru and Norbert and we will slowly add some backends. But see my first sentence.
Appenders in Log4J describe an end point to send the log data/ event object to.
So you can have a rolling_file , socket TCP connection, MQ , DB table , console ... any you need, many already provided with their custom code to pipe the info to the end point.
Appenders are now configurable ( in code ) typically in XML to be able to pipe it to a file in Production / or a DB . While in dev it is to the console.
You can have the same log sent to multiple Appenders with events filtered logically for each of them, with one of the Appender getting the whole dump of events.
The critical issue in logging is performance impact of logging too much.