Which chat option? Also some commands.

Which option? App based or web based?
If you're looking for flexibility and options, go with an application such as mIRC. It allows you to change the interface, connect to multiple networks, log chat etc. mIRC is just one application you can use to connect and is free. After 30 days, you can still use it but you have to wait about 5 seconds to be able to click 'continue' to use it.
If you're looking for something portable and 'light', use the web based client. It does allow you to join other channels, networks and such just not as flexible as mIRC. Do know that it requires java (not javascript) to run, so you'll need that.

Connecting with mIRC
This wont go into detail about extra features as logging, just connecting to the channel.

1) Start mirc
2) Get past nag screen
3) Tools -> options
4) In the 'connect' area, input your nickname and the alt name. Nickname is what is shown to others in the channel and alt is incase its not available.
5) Press the + next to connect and then go into the 'Servers' option area.
6) Press add
7) Enter any description. This is what will be shown in the servers list for you.
IRC Server: irc.furnet.org
port: 6667
group: leave blank
password: leave blank

Cool

Click add
9) If the name (description) isnt selected in the dropdown for IRC server, select it.
10) press 'Connect to server'
11) Wait for everything to load, you should get a popup. You can delete all the channels in the list if you want, you can choose not to display it or you can add the channel. For this example, choose 'Dont display channels on connect' or something of the like and press cancel.
12) type in /join #zetacreations
13) You are now connected.
14) This is optional, but I highly suggest you register your nick. Read the commands to see how.

User op(erator) levels
Users can have op status with varying levels. They are as follows (from highest to lowest).
~Name
This defines the owner of the channel. Usually referred to as QOP. Root QOP can set others as QOP and all lower. Non-root QOPs can only set lower levels.

&Name
This is a SOP. Slightly less privs than a QOP but can still dish out the hurt. Can set others as SOP (not perm) or set others as aop or less (perm)

@Name
This is AOP. This is the 'mod' status. Gives the person the right to ban, voice etc. Can set others as AOP (not perm) or set others as vop or less (perm)

+name
This is VOP. This is voice status. Nothing nifty comes with this except the + next to the name and the ability to chat when the entire channel is muted.

Useful commands
This is all assuming you use mIRC!

/nick name
Changes your display name to name

/msg nickserv register password email
Register your current nick with the password. Email is required to verify.

/msg nickserv identify password
If your nick is registered, whenever you connect to the server you must identify else it will kick you from using that nick!

/whois nick
Gets info on someone

/query nick message
Sends a private message to nick with message. It also opens up a private chat window. Same as double clicking someones name in the user list.

/join #channel
Joins channel. Be sure to have the # sign in there.

\me text
If you did \me is really cool and you should send him all your money it would look like:

* Talarath is really cool and you should send him all your money

I had to replace the / with a \ in the non-examples so it wouldnt be parsed by the forum as a command. Use the / on irc.