log4net has three major objects that we need to be concerned with—the LogManager, loggers, and appenders. Imagine that log4net is a big bucket into which we throw all of the items we want to log on little scraps of paper. Instead of writing all of these pieces of paper by hand, we use an object called a logger. Loggers are used to classify and organize information as it is added to the bucket.
Once we have our information in the bucket, we need to get it out somehow, so we use an appender. Appenders take information from the bucket and "write" it out somewhere, depending on our configuration.
Multiple appenders can process the same log event and handle it in their own way. A couple of good examples of this are a Rolling File appender and an e-mail appender. If, for example, a high priority event is logged (such as a critical application error), then we may not only want to log it to a file, but also e-mail it to an administrator. We can configure appenders for each of these...