If you’ve tried to watch an NFL game at all this season, chances are you’ve already seen the commercials many, many times over: Some dude in a knockoff jersey got rich playing daily fantasy and you can too. But what exactly is daily fantasy and how did it become so popular so quickly?

Daily fantasy leagues have gone from a sports-nerd novelty a few years ago to big business today. The two biggest companies, DraftKings and FanDuel, have spent tens of millions of dollars on advertising in 2015 alone. According to the Boston Globe, DraftKings Inc. has aired more than 25,000 ads across the nation, that’s more than any other brand, in any industry, period. The term “ubiquitous” hardly covers it. Despite a backlash beginning to brew against the onslaught of advertisements, the practice seems to be working.

Thankfully, DraftKings CEO Jason Robins has told the Wall Street Journal that the bombardment of advertising is a matter of striking while the iron is hot and not something the company intends to maintain throughout the season. “This is not something that is year-round for us,” he said. “It’s a brief window where you can fish when the fish are biting.”

However, the sudden high profile of daily fantasy competitions has many questioning the legality of the practice and how a service in which players bet real money on the outcomes online is able to get around the restrictions that tie the hands of other online gaming platforms. A 2006 law allows the companies to classify the games as skill-based due to the knowledge of the sport that is required to play. Specifically, it’s an exemption to the Unlawful Internet Gaming Enforcement Act that allows for an exception to fantasy sports citing that the games “reflect the relative knowledge and skill of the participants.”

This focus on skill is also what the fledgling eSports industry is banking on as it looks to make its way into the big time on the floors of Las Vegas alongside traditional machines and card tables. Fortune reports that even Dallas Mavericks owner Mark Cuban is unable to stay away from the allure of eSports and recently invested $7 million in Unikrn, a Seattle-based start-up.

The worlds of both video games and gambling have long overlapped and now the accessibility of casual gaming and the convenience of modern technology take the casino to the palms of players hands (rather than, you know, the Palms Casino Resort in Vegas). Betfair is one online platform that has taken advantage of the decline of gaming in traditional casinos in favor of mobile apps and a vast selection of games. By offering a much wider variety of options and variations on simple, classic games like slots and card tournaments on smart devices and computers alike, fans find themselves less inclined to travel for the same experience.

Las Vegas is desperately trying to bring many of these people back into the fold by increasing their own digital offerings in their very real brick and mortar establishments. According to the International Business Times, the 2015 Americas Championship for Blizzard Entertainment’s popular “Heroes of the Storm” game was recently held in Sin City and is sure to be only the first of many eSports tournaments that will be held there. With the rapid expansion of both markets, eSports and daily fantasy are now looking to each other for the next big thing. The smart money is betting on them both to win.