With IRC, you can see more quickly what the other person has typed (versus regular Web-based chat where you have to "refresh" your screen to see new typed words. Some Web chat programs do that for you every fifteen seconds). Like Web chat, you can use IRC to have conversations with many people or with just one other person. Also like Web chat, the general topic for each "channel" is predetermined.
Or perhaps you miss hearing the sound of your friend's voice and you just want to call him (or her) up on your DialPad.com Internet phone. That is, using your computer (with your Internet connection) to make long distance phone calls for free AND without going through the phone company!
Want to see the person you are having this chat with? No problem! Inexpensive video conferencing has also come to the Web with products such as CUSeeMe. You can not only hear the other person's voice but you can see them on live video as well! (Assuming both people have the video camera and special software needed!)