Handle requests simple means that when you click on an external (to your own local computer) link, a service (what a server consists of) will send you what you want, in the most basic nut shell explanation I can find.
The main reason why Tomcat's used or what it can be capable of, is when you want to build enterprise applications for the web, what I mean by that is, when you're building web apps and it's a massively critical application to your business you are working on, say a sales chat portal on a site that's been written in servlets (what a type of implementation of J2EE is) allows you to then add additional features, whilst the applications running and not having to take your app offline at any point, if you have programmed it efficiently, then when the new feature(s) are ready to be put online or sent up to the server they just add themselves to the already running application.
It's like a truly enterprise operating system like Linux RHEL will try to keep old functions and add new ones, to keep the older users using their operating system, but allowing more features to be added, sometimes though as I have found out that's not always entirely possible in the sense of additional software but in the actual Operating Systems functions for programming like glibc for example there will be the old native functions as well as the newer ones.
That's really one of many of the bigger reasons for using Java Enterprise Edition capable services, like Tomcat is one major player within that need within IT services.
Last edited by j.smith1981; 18-09-2012 at 18:46.