Difficulty understanding nodejs documentation - node.js

Question

I'm really confused about this section
http://nodejs.org/api/http.html#http_http_createserver_requestlistener
The requestListener is a function which is automatically added to the 'request' event.
What does the term "added" specifically mean?
Also for here
http://nodejs.org/api/http.html#http_event_request
What does the the code directly beneath mean function (request, response) { }? Does it mean that that function gets passed each time there is a request?

Answer 1

The requestListener is a lsitener that listens to the 'request' event. Each time a request event is emitted, the requestListener is executed. You pass a function.
That function you pass, should match:
function (request, response) { }
I believe there is an example at the main page of nodejs.org.
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello World\n');
}).listen(1337, '127.0.0.1');
console.log('Server running at http://127.0.0.1:1337/');
So each time a request-event is emitted, this function is 'called'.
function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello World\n');
}
With req and res a parameters. (Request and response).

Answer 2

If it is any help the statement
var app = http.createServer( function reqlistener(request, response){...} ).listen(1337);
where the function reqlistener is the requestListener argument, is equivalent to the following
var app = http.createServer().listen(1337);
app.on('request', function reqlistener(request, response){...} );
So it is just a shortcut for providing a listener for event request during server start itself. The event request is emitted for each request once when received by the server.