What do Lebron James, Lionel Messi, and the online persona "Trixi" have in common? They're all professional athletes.

Trixi's professional sport is Defense of the Ancients 2 - an online video game. Video games have made an unexpected and expedient stride into the professional sports arena as sponsors, consumers, and money are lavished on teams and players.

Known as electronic sports (or eSports), video game tournaments can host hundreds of thousands of spectators via live streaming. They pack halls and live events can get sold out, such as when a League of Legends (LoL) tournament sold out Los Angeles' 18,000-seat Staples Centre last October.

Tickets at Seattle's 17,459-seat Key Arena were sold out for The International DOTA 2 Championships on July 18 [EPA]

The most recent craze in eSports came from a tournament called "The International" - the world championship of DOTA 2, which took place in Seattle's Key Arena last week. This year's The International had a prize pot of nearly $11m, half of which was reserved for the winning team - more than the pro-golf US Open and as much as Europe's UEFA champions league winners. The tournament has blossomed since its start in 2011, when the total prize money maxed out at $1.6m.

At The International, two teams battle it out on a map where the object is to destroy the other team's base. Each match can end in as quickly as 15 minutes, or can extend for over an hour. The advancing team has to win two out of three matches. Newbee, a Chinese team seen as an underdog prevailed, winning the competition.

At the height of the tournament, nearly 800,000 viewers watched a match online at once, and the entire tournament saw 40 million page views on Twitch, a live streaming site. The finals were also broadcast live on ESPN.

ESports have become increasingly popular across the globe. "In South Korea, eSports have become a huge part of the country's culture. In countries like the USA, Brazil, Poland and Sweden, eSport is also highly accepted," Alex Pfeiffer, head of the Centre for Applied Games Studies at Danube University in Austria and author of eSport - eine Analyse von kompetitiven digitalen Spielen, told Al Jazeera.

Games, games, and more games

However, eSports consist of several different genres. They can come from games such as DOTA, or they can be real-time strategy games - like Starcraft 2 - or even first-person shooters, such as Call of Duty.

DOTA 2 and League of Legends, for example, are multiplayer online battle arenas (MOBAs), where each player controls a "hero" and must gain experience killing enemy soldiers - called "creeps" - and the other team's heroes. In the lower left-hand and upper right-hand corners of the map reside each team's base. The map is then symmetrically divided along three lanes where waves of creeps advance to the other side. The players can only control their heroes, and must work together to gain experience, acquire gold to buy in-game items like daggers and special spells, and kill enemy players. Players can pick from over 100 heroes, where they must balance between support heroes, to more tank-like heroes that can take and deal heavier damage. If a hero dies, it then gets resurrected after a period of time, depending on the hero's level. There are five players on each team.

Starcraft 2, a futuristic real-time strategy game requires players to build armies [AP]

"You have different roles in DOTA. There are five players and each player has a different role. Two players operate as supports, and their goal is to accumulate experience, level up, and scout," said Sahil Deva, a manager for the profession DOTA 2 team Fnatic, which participated in The International.

Fnatic is an eSports organisation that hosts, trains, and promotes several teams across a wide spectrum of electronic sports.

"Then there's the midhero. The midhero runs the midlane, the place where the most creeps come from, which allows the hero to get the most experience and gold. Midheroes gain experience most quickly and they set up a lot of kills. Then there's the offlane hero, the person designed to work the longest lane, and is built to kill heroes. The last hero is the carry, who starts out weak, but becomes progressively stronger in the later stages of the game," Deva said.

Another professional electronic sport - Starcraft 2 - hails from the resource management real-time strategy genre (RTS), where players own a military, collect resources, build structures and military units, and wipe out the enemy base.

Pro-athletes?

Each game requires a well thought-out strategy, as well as split-second decision making and teamwork. But can they be called a professional sport akin to football, basketball, tennis, hockey, and chess?

"Our players need to train for eight hours a day, they have to eat well, and they need to be psychologically well. They're professional athletes in terms of honing in on their hand coordination skills, using the mouse, and very quick thinking," Anne Mathews, a founder and the finance director of Fnatic, told Al Jazeera.

In the documentary "The Hax Life", a film that revolves around Starcraft players in Korea, a player describes how each pro-gamer must execute up to hundreds of actions per minute (APM) on the keyboard and mouse to win a game. "[APM] is an average rate on how quick your fingers move. It is a rate that shows how quick you can draw your picture in the game with a keyboard and mouse. To win a championship, it should be at least over 200, or in the lower 300s," he said.

ESports players are beginning to get the same legal footing as other professional athletes as well. The US issues the same visa to pro-gamers as they do to players of other professional sports. South Korean Starcraft player Kim Dong-hwan was given a five-year P-1A visa to play in the US. Canadian LoL gamer Danny Le managed to attain the same visa. Even a university in Illinois offers athletic scholarships to gamers.

"Sport is a field of cultural activity, in which human beings voluntarily establish a relationship with other people, consciously intending to develop their abilities and accomplishments - in particular in the area of skilled motion - in order to compare themselves with other people, according to rules set by themselves or adopted on socially accepted ethical values," Pfeiffer told Al Jazeera.

"Split the definition in all its small parts, like cultural activity, voluntary, relationship, skilled motion, and you will quickly see that eSports fits 100 percent within the definition of sport. ESport professionals have to train like all other athletes through tactics, fitness and on the game," he added.

'Show me the money'

Games are extremely entertaining to play as well as to watch and spectate. The ability to spectate means you have viewers - and sponsors can see viewers as potential consumers. - Sahil Deva, Fnatic manager

In conjunction with pro-athlete status, gamers and teams make some serious cash. Much of the money comes from top-brand sponsors, such as Coke, Red Bull, and T-Mobile. Computer companies, custom keyboard manufacturers, and energy drinks also sponsor teams and leagues. They first became attracted to eSports from live streaming websites, like Twitch, that host free viewings of the competitions. In fact, Twitch has become so popular among gamers that Google bought the site for $1bn.

"Games are extremely entertaining to play as well as to watch and spectate. The ability to spectate means you have viewers - and sponsors can see viewers as potential consumers. As viewership grows, so does the amount of sponsors that see people as consumers," Fnatic's Deva told Al Jazeera.

The number of viewers at these competitions regularly reaches into the millions, according to Mathews. As a result, "there's big publishers that put up big money to host tournaments", she told Al Jazeera.

"Sponsors like Samsung spend a huge amount of money on all kinds of eSport activities. ESport players/athletes are treated as stars," said Pfeiffer.

"The real growth in eSports is being driven by advertisers who are buying commercial time on premium eSports broadcasts on MLG.tv and other broadcast outlets. This is an important distinction because these advertisers are moving money from traditional channels like television to eSports' online broadcasts in order to reach the highly-engaged, affluent young men who are deeply interested in eSports. Through MLG.tv, advertisers are able to reach this difficult to find audience over the web, consoles, and smart phones, anywhere they are connected," Mike Sepso, Major League Gaming's co-founder and president, told Al Jazeera in an email.

An evolving genre

Major League Gaming, another eSports organisation, reported that 85 percent of all viewers are male.

Deva thinks the issue is generational. "Before, boys traditionally played video games. I think that's getting much less these days. Games are becoming much more open, and women have started to pick up gaming," he told Al Jazeera.

The main issue currently facing eSports is the lack of an independent regulatory body that commissions rules, regulations, and a code of conduct.

"We need to establish a professional body and we have to establish it quite urgently," Mathews said.

"There are referees; but they are brought by the game publishers. What is needed is a professional code of conduct created by an independent organisation," she added.

In the meantime, eSports are likely to increase in popularity.

"In five years, many more games will be made specifically for eSports. The sport will be significantly more mainstream and a key conversion will happen - fans who don't actually play the games will outnumber fans who do. Viewers will outnumber participants which is the case in traditional sports now, but not so in eSports," Sepso said.