Sorry for my ignorance here, but when I hear the word webserver, I immediately imagine Apache, although I know people use Microsoft\'s IIS too. However since I\'ve been hanging
Glassfish will soon release the modular kernel.
This means that the containers you need start up and shutdown as you need them. I.e no EAR deployed, EJB container won;t start up. This seems to have made it very good for development as it can start and stop very quickly. This takes it a lot closer to development environments like Rails (where redeployment is a massive part of your development)
The need for a seperate Web server is mostly needed in a production environment. You would normally find a Application server to be suffice most of your development needs. A web server is capable of holding larger number of active sessions and connections, thus providing the necessary balance without performance costs.
Stick to a simple web server if you are only working with servlets/jsps. It is also to be noted that in a netbeans environment, glassfish has better support than other App servers. In the context of eclipse though, WSAD and JBoss seem to the preferred options.
GlassFish is an Application Server which can also be used as a Web Server (Http Server).
A web Server means: Handling HTTP requests (usually from browsers).
A Servlet Container (e.g. Tomcat) means: It can handle servlets & JSP.
An Application Server (e.g. GlassFish) means: It can manage Java EE applications (usually both servlet/JSP and EJBs).
You should use GlassFish for Java EE enterprise applications.
I have used GlassFish server for developing Web Services. It provides a very interactive Admin Console where admin can test the Web Services. I really find it helpful while developing Web Services