WebServer Vs ApplicationServer Vs Servlet Container

[kri shan]

In the recent version of Tomcat(Servelt container) supports connection pooling and many other new features as Application Server. Whether i need expensive Application Server than cheap WebServer(HTTP) + ServletContainer(Tomcat) ?

[Bear Bibeault]

How can we tell you what you need if you don't tell us what you want to do?

[Hussein Baghdadi]

Where is the question?
Not to mention the subject of the post is confused.