Internet Relay Chat was, until recently, the domain of people who weren't necessarily involved in "surfing", or looking at websites like this one - or indeed any of the millions of others there are.
In the traditional "chat rooms" you need to use a special variation of what is essentially a space in which to type, like the "terminal" in a Windows operating system. As more and more people have become involved, it has become possible to find smart little computer programs running under 'windows' or similar looking operating systems that have created 'helps' in their menuing systems that take away a lot of the need to remember command line instructions that you have to use to communicate with others in what is essentially little more than a teleprinter (teletype) window.
For those who might wonder, there are these "chat client applications" for each of the different types of computer there are, whether "Apple-Macintosh", or whether genuine IBM running its fabulous operating system called OS/2, or more recent IBMs and nearly all the pretend IBMs which run one or another version of Microsoft's Windows (which they adapted from the IBM system anyway, though will never admit they did!).
Java is just a way of writing one standard set of instruction code so that computers of absolutely all types will understand and execute the commands given to them. Until the concept of Java came into being, every program that was needed to work on more than one kind of computer had to be rewritten to suit a new type; this is called porting. This made interchanging programs between different kinds of machines nearly impossible, and caused the situation where you have no choice but to buy somebody's expensive operating system in order to run a particular program that doesn't run on any other system.
This portability of java applications has (generally speaking) caused programs written in it to run slower, but in time developers will improve the speed of Java applets (an applet is just a little application, or little program).
Java has been around for several years, and is currently the subject of legal arguaments between its developers, Sun Microsystems, who created it to eliminate the problem just described by allowing all programs written in it to work accurately on any operating system on any kind of computer, and Microsoft, who have rewritten parts of Sun's code to make it not work on anybody else's system except those they sell! This statement is a simplistic generalisation, but it is basically true; you don't really need to know more than that at this point. However a practical example of the problems caused is that the two main Web Browsers - Internet Explorer (Microsoft) and Netscape Navigator (not Microsoft) do not read java in exactly the same way.
Incidentally, most of the IRC chat organisations now have web pages, so it is really getting integrated at last!
Whichever type of chatting you decide to do, you will find there are rules. Some of the rules relate to what the server or the channel owner allows you to say (type), how much stuff you can type in one lump, and general disciplinary things like if you don't like the rules of the channel, you have to go somewhere else because you are made to feel unwelcome if you persist in trying to be smart. Channels and servers have operators whose task is to ensure that those who refuse to keep the rules are disconnected from the channel or the server. Some of these operators are humans, members of the chat community. Some are automated computerised identities, known as bots - short for "robots".
The term "operator" is less frequently used in the java chat rooms, where the term "Moderator" is more frequently found. The words can really be used more or less interchangably. In reflection, the term Moderator is probably a better one, as the name operator may well stem stem from days long-ago when operators would also be involved in switching connections as in manual telephone exchanges. Military networks' operators still have that function. I believe the term supervisor is really more appropriate. There are also those whose function is to supervise networks and servers rather than channels - on irc these are still called "ops", this time ircops. It is important to realise that these people are all, without exception, volunteers, who give of their time and expertise for the benefit of the rest of us so that we may have a hassle-free environment in which to chat, whether it be just a reminiscing yarn or an instructional session, or anything in between.
The channels are like floors in an apartment block, and you can walk in through the front door (the server), and climb the stairs to the appropriate floor, knock on the apartment door, and you have gone into a channel. This is over-simplifying it, but it's a good way to describe it without getting bogged down in too much detail...
While I have steered you towards this particular network, there are many others, in no particular order, such as dalnet, efnet, ircnet, webnet, xnet, and even an "othernet"! (lol - laugh out loud).
Another good idea would be to look at the website of one of the designers of chat clients, and the one I like - mIRC - has a wealth of information on the sort of things that are useful to know when you are connected, including a glossary of instructions that you can type that will cause the server to return information to you that may be useful.
Then there's Java. There are several different organisations that have created Java applets to run on web pages, and perhaps the easiest site to read about them is that belonging to the chat division of Paralogic Corporation.
The "old original" method requires you to use a seperate chat client such as mIRC, and once it is running, you can find a direct link on its opening page to the net of your choice. Just scroll the list of nets until you find the one you want, in this case Undernet, press the connect button, and away you go. You will then need to join the channel of your choice, and most chat clients have very good help information to explain how to do that and other related things.
A few chat networks have access from both java applets in the world wide web AND the more traditional IRC facilities.
If you would like to try out regular IRC using the web browser on which you are looking at this page, you can take a link to several java sites... go to this site and choose which channel you wish to join on which network. It will open in a seperate window so you won't lose your spot here. The ones on that server system with which I am associated are #Christian and #Christian-Chat (my own).
Not all IRC systems are accessible from the World Wide Web. It loads slower than using a proper chat program because thats normal with java, and will sometimes lag too, but that's also a feature of IRC and the way servers are connected.
I hope that this page has answered some of your questions. May I suggest that if you have more, you pursue the information pages associated with specific channels, and I point you to that of the main IRC channel I participate in, that of starlink-irc's and undernet's #christian, which you can find on the web at http://www.chatministries.org, for which there is a link here. Even if you don't have further questions, it will give some idea of what channel management expects of those who come to visit them.
You might like to have a look at a web page of photos of some of the folk who regularly meet in the starlink-irc/undernet christian chatrooms.
There is a link here which will take you to mIRC's home web site from where you can download the product and use it. It is shareware, which means you should be ethical and pay ten English pounds to its author if you decide to continue using it after a month. Please read my page about "shareware".