When it comes to video games, "League of Legends" is in a league of its own.

The popular online PC game, launched by publisher Riot Games in October 2009, is hitting its 10th anniversary.

Typically, after a decade a is likely to have been retired—a victim of technological advances and competing releases. However, even though relative newcomer shooters such as "Fortnite,""Apex Legends" and "Overwatch" get a lot of attention, "League of Legends" maintains plenty of clout in the growing esports arena.

Riot Games holds an online celebration today with prizes being awarded to players within games, special matches being broadcast on YouTube and Twitch, and a 10th Anniversary livestream event to announce upcoming new features and changes coming to the game.

If you aren't familiar with "League of Legends," here's the basics on the strategy role-playing game: Two teams of five "champions" compete to take down the other team's base. Your goal is to destroy the other team's big hitters, while evading a slew of computer-generated minions and rapid-firing turrets on your trek towards their base.

It sounds simple, but there's much more to the game, which falls into the multiplayer online battle arena (MOBA) genre. "It is probably the closest thing to taking chess out of the physical environment with all these additional layers of critical thinking on top of it," said Ann Hand, CEO and chairman of Super League Gaming, a national amateur esports organization.

"The type of skills it takes to be exceptional at that game, not only make the game challenging and enticing to have that longevity, but also those skills are extremely transferable into other life interests," she said.

Millions play—and watch—'League of Legends'

At some point each day, the number of players engaged in the game—also referred to as "League" and "LoL"—hits 8 million players online at the same time, making it the biggest PC game in the world, Riot Games says. Overall, about 100 million play the game each month.

You can play for free, earning upgrades for your characters as you gain experience. But you can also spend money for upgrades, too. Overall, the game generated about $1.4 billion in revenue in 2018, according to Statista.

"League of Legends" draws a gigantic crowd of spectators, too. One of the most watched games online—whether it's simply viewing good players streaming their games or actual esports competitions—"LoL" amassed 69.7 million viewing hours on Twitch in August 2019, more than any other game, and was also the highest-viewed game on YouTube with 17.8 million, according to research firm Newzoo.

'League of Legends' helped spawn esports

While there were organized competitions between professional gamers before "LoL" came along—on games as diverse as "Halo" and "StarCraft"—Riot Games helped establish esports, a business that is expected to grow globally from $980 million this year to $1.8 billion in 2023, research and consulting firm PricewaterhouseCoopers estimates.

"The developers, the game makers, they did not support the leagues and the tournaments and the maturity of that (early) ecosystem," said Steve Arhancet, a former professional gamer and co-CEO and owner of Team Liquid, a pro esports team with athletes who compete in several games "League of Legends" included.

"They were one of the first developers to say, 'Hey, we are going to bring this in-house and run and create a formal league like the NBA or NFL. That was a first," he said. "They saw it as a way to continue to market their game and bring users back to playing."

Today, there are more than 100 professional "League of Legends" teams with 800-plus pro players in 13 leagues across the globe. Each year's matches lead up to a World Cup-style competition. The 2019 League of Legends World Championship, which kicked off on Oct. 2 in Berlin, culminates Nov. 10 in Paris at the AccorHotels Arena, which will also host events in the 2024 Summer Olympics. You can watch the action on watch.lolesports.com/home. Last year's event drew more than 99 million viewers.

Prizes in the millions

"League of Legends" is also one of the most lucrative esports games, holding the Nos. 8-10 spots on the top ten esports prize pools, according to ESPN esports. Last year's World Championship holds the No. 8 spot at $6.5 million, and this year's is expected to surpass that. (The pool starts at $2.2 million and increases based on sales of in-game items during the tournament.)

The game with the biggest prize pool? That's another MOBA, "Defense of the Ancients 2," or DotA 2. Its 2019 International awarded $34.3 million in prizes, eclipsing the 2019 Fortnite World Cup, which had $30.4 million in prizes, the second-biggest prize pool so far. "Dota 2" also holds the No. 3-No.7 slots on the list.

'LoL' has gone mainstream

Earlier this year, Riot Games collaborated on an episode of "The Simpsons," called "E My Sports," in which Bart becomes an esports star and travels to South Korea for a big-time competition.

More recently, "League of Legends" became part of a storyline in HBO's "Ballers" series, starring Dwayne "The Rock" Johnson.

'League' continues to evolve

Before they co-founded Riot Games in 2006, Marc Merrill and Brandon Beck were USC students who had become disillusioned by the game industry's model of selling $60 packaged games, which were often abandoned after a few years for sequels or other releases.

"Just like millions of others, we felt (like), 'We don't want the next version (of the game) ... improve this one," Merrill told U.S. TODAY in an interview. "With that deep understanding and pain from a player standpoint we thought that the game industry was going to be evolving to have this direct relationship with players and with the community."

Inspired by games such as "World of Warcraft," "Starcraft" and "EverQuest," they decided to create their own game that could be constantly updated. As interest in "League of Legends" grew and people began to watch others playing, Riot Games built out an "esports ecosystem" to foster competition and viewership, Merrill says.

But the esports aspect grew out of his and Beck's desire, Merrill said, "to deeply serve and nurture a community that we were part of and could deeply relate to."

Speaking of nurturing, each year Riot Games updates the game soon after the World Championship has ended. Already, the development team has said changes are coming to Summoner's Rift, the game's main battle map, in November.

Updates about that and other news will be part of the special 10-year anniversary live stream, which begins with a pre-show at 8:30 p.m. ET/5:30 p.m. PT. You can watch on RiotGames.com or the Riot Games Twitch channel and League of Legends YouTube channel . There will also be in- events for those playing all day, as well as special matches broadcast on Twitch and YouTube.

"We're excited about the future of 'League of Legends," Merrill said. "At 10 years in it's incredibly healthy and we're just getting started."