Online Gaming (Networked via the consoles)

Xbox Live is an online multiplayer gaming and digital media delivery service created and operated by Microsoft Corporation. It was first made available to the Xbox video game console. An updated version of the service became available for the Xbox 360 console at that system's launch. Games for Windows - Live makes certain aspects of the system available on Windows Vista PCs, with plans to extend Live to other platforms such as handhelds and mobile phones as part of the Live Anywhere initiative.
basically... its a neworking system that can allow all owners of Xbox 360s and an internet connection to play anyone else in the world on the same game. (For a small fee annually)

PlayStation Network, often abbreviated to PSN in the gaming community, is Sony's free online service provided for use with their PlayStation 3 (PS3) and PlayStation Portable (PSP) video game consoles. As of February 14, 2008, there are over 2.9 million registered PlayStation Network accounts in North America.

The Wii console is able to connect to the Internet through its built-in 802.11b/g Wi-Fi or through a USB-to-Ethernet adapter, with both methods allowing players to access the established Nintendo Wi-Fi Connection service. Wireless encryption by WEP, WPA (TKIP/RC4) and WPA2 (CCMP/AES) are supported. AOSS support was discreetly added in firmware update 3.0. Just as for the Nintendo DS, Nintendo does not charge fees for playing via the service and the 12 digit Friend Code system controls how players connect to one another. Each Wii also has its own unique 16 digit Wii Code for use with Wii's non-game features. This system also implements console-based software including the Wii Message Board. One can also connect to the internet with third-party devices.
The service has several features for the console including the Virtual Console, WiiConnect24, Internet Channel, Forecast Channel, Everybody Votes Channel, News Channel and the Check Mii Out Channel. The console can also communicate and connect with other Wii systems through a self-generated wireless LAN, enabling local wireless multiplayer on different television sets. Battalion Wars 2 first demonstrated this feature for non-split screen multiplayer between two or more televisions.

So in simple terms... wii users can connect to the internet. As with the PS3 the service is free, and users can play and compete against other same console users for highest ranks or just for fun!

Wireless online networking has revolutionised the gaming world. Connecting gamers with same interests and influences all over the world. Multiplayer no longer means forcing your (bored and unenthusiastic) relatives to play against you. It is now combining with the online instant messaging too. Players can use company constructed (eg. EA sports messenger) instant messaging services similar to the world renouned windows live messenger (MSN messenger).