Next to e-mail and surfing the Web, chatting is the most popular pastime on the Net. You can chat with using either IM or IRC. And like most of the things on the Internet that people get mixed up, IM and IRC appear to have a lot in common. Both allow you to create private chat rooms with close friends and both work without launching your Web browser. But the similarities end with appearances.

IM stands for Instant Messaging, and IRC stands for Internet Relay Chat. IM is a service that a company like AOL offers. IRC is a network of computers. IM is more like immediate email than a chat room -- instant messages (IMs) appear instantaneously on your friend's screen when you hit the send button.

Unlike IRC, instant messaging has become one of the most popular activities on the Internet for kids and some adults, because IMs are faster than email, but less crowded than IRC chat rooms. In other words, instant messaging is a good way to have a quick conversation.

Instant messaging uses the client-server model to work. Your client software connects to a central "server" that verifies your identity and registers you as being online. Then other users who are registered and connected to the central server know that you are logged on because the server tells their client software. The instant messaging software will require you to either enter in a screen name or email address. This is how the server is able to track who is online.

But, IM is not without controversy - some people feel it is an invasion of privacy and annoying to always have someone know when you are online. These are valid criticisms, but you do not have to start or launch your IM software client when you go online if you do not want to chat. IM is like television, you can turn it off.

With that caveat stated, we cannot ignore the fact that the technology of instant messaging is finding its way into many of our lives. Businesses have decided that they want their employees to use instant messaging software, so that employees in different offices can quickly communicate without picking up the phone or still be able to answer a quick question even if they are on the phone without putting a customer on hold. Companies have found that instant messaging is a very cost-effective and convenient way to stay in touch with travelling employees.

Instant messengers have also touched the hearts of families by creating a great way to stay in touch with a child who is away at university without breaking the family budget.

So, which IM software should you use?

AOL IM also known as AIM?

ICQ, pronounced "I Seek You"?

Yahoo! Messenger?

MSN Messenger?

All of the IM software clients described in this article are free. You can just download them off the Web. They all let you set up your own private conferences to chat with multiple people, transfer files like photos, and if your computer has a microphone set up, you can use IM clients to "voice chat" just like you would on a phone or make PC-to-phone calls.

America Online started the Instant Messaging craze with their popular buddy list that they originally integrated into America Online. Then they introduced AIM, the free instant messenger that allowed you to communicate with users on AOL even if you were not a member. People were ecstatic. That was a few years back and still today AIM remains one of the most popular clients used today.

The big advantage of AIM (www.aim.com) in my opinion is that is easy to use, especially if you have never chatted before. It is easy to find out if your friends use AIM, too - all you need to know is their email address. You also do not have to worry about strangers trying to chat with you when you use AIM because you can control who is able to communicate with you by using the available buddy privacy features. You can also check your email using AIM without having to open your email software.

But, there are no "invisible" features so everyone on your buddy list knows when you turn on AIM, so do not start it if you do not want to chat. Another disadvantage is that there is no firewall support. You must configure using HTTPS to make it work through firewalls and proxy servers - you cannot use AIM at work without permission.

While AIM is the easiest instant messenger software, ICQ (www.icq.com) is the most complex instant messenger. With that complexity, ICQ is jam-packed with features, and it basically has all of the features that the other IM clients have. If you are busy and do not want to be disturbed you can select the "Invisible" mode so no one knows if you are online, or the "Not Available", or "Do Not Disturb" mode. If you are working hard on a report and want to receive messages from your boss, but not your sibling who likes to chat, you can make yourself invisible to your sister, so she will not see you online.

My favourite feature is that ICQ saves your messages for you like an answering machine when you are offline. ICQ also lets you page someone, and if the person you are paging has a pager that supports text messaging, then you can send a text message, telling your co-worker that he better get back from lunch because a meeting is starting now. ICQ also has built in firewall support so it is easy to set up behind a company's firewall.

Even with all its features, ICQ has drawbacks. It's hard to set up and figure out what's what because there are so many options. ICQ is also a big program (compressed it is still 6 MB, so it can take awhile to download) and it hogs more RAM than any other IM client.

The other 2 big IM software clients are provided courtesy of two of the biggest Web sites that offer free email, Yahoo and Hotmail..

MSN Messenger (http://messenger.msn.com) The MSN Messenger Service is Microsoft's answer to the ever-popular ICQ and AOL Instant Messenger clients. You no longer need a Hotmail email account to use MSN -- you can now register with your own email address, although you cannot read your email with MSN Messenger unless you have a Hotmail email account.

MSN Messenger has a lot of the same features as the more complicated ICQ software. MSN Messenger lets you control who can tell that you are online and which people can send you messages at any given time. MSN also supports "text messaging", which is techy jargon for sending a message to someone's pager or cell phone. And liked ICQ, MSN Messenger also has a built in firewall. But, unlike ICQ, MSN messenger does not allow you to send messages to someone if they are offline.

People that chat a lot complain that it is hard to find people using MSN if they do not have a Hotmail email account, and there is no "random chat" on the MSN Web site, like the Yahoo and AOL chat rooms where you can chat with strangers, so you cannot meet anyone new.

Yahoo Messenger (http://messenger.yahoo.com) is the latest instant message client and has recently become very popular because you can use it for video conferencing if your computer has a webcam connected to it. Another handy business feature of Yahoo Messenger is that it automatically archives your conversations, conferences and alerts, so that you have a record of what was said without taking notes.

There are two big drawbacks. The first is that you have to set up a Yahoo email account (myname yahoo.com) to use it, and even though it is free email, you might not want another email account. The second drawback is that you cannot control who knows you are online, or in IM jargon, you cannot control "who you are invisible to". Either all of your friends can send you messages or none of them can.

My biggest complaint is that I have three different IM clients on my computer: My cousins use MSN Messenger to keep in touch, the company I contract for wants its employees to use AIM instead of picking up the phone, and my friends chat with Yahoo Messenger. I like diversity, but a bit more interoperability is definitely needed. Although instant messaging is inexpensive and fun it has not made my life less complicated.