I\'ve installed nodejs and ran couple of simple examples like opening a server on a port and listen on that port.
However, I still can not relate nodejs to web develop
First Just try to implement basic application and get a feel of the framework. There are several tutorials online for example:
http://net.tutsplus.com/tutorials/javascript-ajax/learning-serverside-javascript-with-node-js/
Documentation at http://nodejs.org/
http://howtonode.org/
Also there is a 70 min screencast by peepcode which costs 9$
https://peepcode.com/products/nodejs-i
There are also several apps on github, which you take a look at. Reading code is always the best.