Currently Being ModeratedMar 29, 2013 2:20 PM (in response to Armand56)
FaceTime is available for Snow Leopard and comes included in later versions of the OS.
It uses an Apple ID to "register"
You can then Video Chat 1-1 with other FaceTime Macs or to iPhone and other Camera equipped iOS Devices.
It is a one trick pony that only does 1-1 video using your Address Book and Apple IDs and Phone numbers as Contact points
iChat is an app that became A/V capable in 2004 with iChat 2
It can do Text Chats, Audio only Chats (up to 10 including you) and Video Chats (Up to 4 ways including you)
Later versions have Video Effects and Backdrops as extras along with iChat theatre which can displays pictures as singles and Slide Shows or "Documents" for other apps such as a Powerpoint or Keynote presentation.
At iChat 4 you also get Screen Sharing.
Chats are to "Buddies".
Buddies are contacts arranged in Buddy Lists with a Buddy list dealing with one service at a time.
So you can join the AIM service with an AIM registered name (or an Apple Issued Apple ID that is suitable ending in @mac.com, @me.com or @iCloud.com)
You can also get a Jabber ID (from various Jabber servers) which include GoogleTalk and Facebook IDs
In iChat 6 (Lion) you can also join the Yahoo service if you have a Yahoo ID.
Only AIM and Jabber will do A/V chats though due to the Yahoo Account only doing Text chats.
On the iOS devices you have Messages for Text chats and there is not Audio option in FaceTime.
At Mountain Lion iChat "becomes" the Messages app on the Mac.
It can do everything that iChat can do PLUS it has the ability to add and Apple ID and "register" it for iMessages - the Apple service that iOS devices use between each other.
It can also be linked with your iPhone Number so that iMessages are then synced across all devices.
It then gives the iPhone the option of sending from Phone Number or Apple ID and the same to the Mac version of Messages.
When making an iMessages chat to a Contact (Uses your Address Book for people to connect to) the Mac Version of Messages has an option to Invoke FaceTime to Video to them.
For AIM and Jabber Buddies it still retains the in-house video features.
Another way to say this.
OS X 10.3 through to OS X 10.7.x have version of iChat.
At OS 10.8.x (Mountain Lion) the app becomes Messages.
Right at thre beginning iChat is AIM only and Text only.
In Panther (OS X 10.3) it become Video and Audio Capable. (iChat2)
At the next version of the OS iChat 3 gets Jabber and some Video and Backdrop effects.
iChat 4 in Leopard gets Screen Sharing and iChat Theatre giving you options to Help a Buddy or Show them something at your end (Screen Shares are an Audio Chat+)
iChat 5 adds little new stuff.
iChat 6 in Lion adds the Text Chat only ability to use Yahoo Accounts.
In Mountian Lion ichat "Becomes" Messages with the ability to iMessage - the new Service from Apple that iOS devices use.
It is Mac to Mac or Mac to iOS device.
An iMessages is text Only.
Like FaceTime it uses your Contacts (Formerly the Address Book) to access their iphone Number or Apple ID to connect to them.
It will Invoke (start up) FaceTime from an icon if you wish to Video.
It also has the ability to use the AIM, Jabber and Yahoo services as in iChat.
All the way though is the ability to do the same thing Mac to Mac on your LAN with a Bonjour account in the Accounts pane of the app's Preferences.
Bonjour is Also Text, Audio, Video and Screen Share chat able.
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.3)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously
Message was edited by: Ralph Johns (UK)