Many commercialized parties offer various tournaments, with competitions in such games as StarCraft, Quake III, Call of Duty 2, Warcraft III, Counter-Strike, Unreal Tournament, America's Army, Battlefield 2, Doom series, and the Halo Series sometimes awarding prizes to the winners. Prizes can include computer hardware such as overclocking kits, cases, lights, fans, graphic cards and sometimes even complete computers (often considered humorous as typically the winner of the competition would already have (and be competing on) a custom PC far superior to the prize).
The duration of the event is not standardized; many organized parties last for a weekend, while there have also been longer and shorter parties such as weekend wars.
Big LAN parties often offer a quiet place to sleep, shower, and eat, as well as hired security, alternative entertainment (such as music), and a dedicated support crew, as well as a professionally managed network including a connection to the Internet. Catering might come in the form of a bar, delivered food such as pizza, or nearby shops. Some parties come fully catered in the form of regular barbecues or even employment of a catering staff running a public canteen.
Gaming clans -- groups of gamers that often play in team games -- often use these gatherings to meet one another, since they typically play together over the Internet between other parties with little real-world contact. Their goal is often to win tournaments. Clans are often in "ladders" where they move up after winning a match. As well as counting for standings in national and international gaming leagues such as the CPL there are regular events such as QuakeCon in which the very best players from around the world compete against one another, much like in popular sports. Practice matches are usually held prior to a match so competitors can get a rough idea of what they are up against.
Some attendees also use these parties for the purpose of file sharing. Copyright infringement via file sharing is often discouraged or forbidden by the larger parties. However, enforcement is rare and spotty due to the time involved and often a lack of desire by organizers. Some LAN parties actively support file sharing for legitimate purposes (game patches, updates, user contributed content), and may run Direct Connect hubs or other P2P service servers. One of the main reasons for running such servers is so file sharing can be monitored/controlled while standard Windows file sharing (SMB/CIFS) can be blocked, thus preventing the spread of SMB/CIFS-based viruses. Most P2P setups used at LAN parties also have a 'centralized' chat area, where all members of the LAN party can converse in an IRC-like environment.
There are also other kinds of parties not referred to as "LAN parties" where temporary LANs are built, but are not used as a main attraction. Amongst these are demoparties such as Assembly and hacker conventions such as DEF CON.
In the traditionally active demoscene countries, such as those in Northern Europe, the LAN party culture is often heavily influenced by demoparties. This is due to the fact that many of the largest demoparties were already well established in the early 1990s and their facilities were also suitable for large-scale LAN party activity. This eventually led gaming clans and other similar groups to attend these events and regard them merely as large LAN parties. On the other hand, it is not uncommon for "pure" LAN parties in Northern Europe to organize some demoscene-like competitions in areas such as computer graphics or home videos.
This article from : http://en.wikipedia.org/wiki/LAN_party