The other day, someone caught a Pokémon on my couch and I was flabbergasted, and a little terrified. What is this suddenly very popular Pokémon Go phenomenon, with the power to send reasonable humans out into the world to catch critters in an augmented reality viewable through smart phones?

1. Pokémon Go works a lot like the 1990s version that was played on a Nintendo Gameboy, with 150 Pokémon currently available to catch and battle against. This time, it’s played through your phone: users wander around in real life, point their phones at stuff, and catch Pokémon. You’ll see a cartoony version of Google Maps that replaces real-life landmarks with Pokémon buildings. As you walk around, your in-game character moves like you do, and bumps into characters you can capture. On the couch, on the train platform, in your Aunt Dina’s bathroom.

2. It’s a joint project by The Pokémon Company, which is 32%-owned by Nintendo, and Niantic Inc., a spinout from Google parent Alphabet Inc, The Wall Street Journal notes.

3. It’s only available in the U.S., New Zealand, and Australia for now, but it’s wildly popular in those markets. As of Monday, it’s at the top of Apple’s App Store charts in the U.S., according to data from Similar Web. It’s already been installed on more Android smartphones in the U.S. — 5.16% of them — than Tinder, which is on 2% of Android phones domestically, Business Insider notes.

“Pokémon Go has gone beyond success to become a phenomenon, topping the revenue grossing charts in the three regions into which it has been launched,” Deutsche Bank AG Analyst Han Joon Kim told Bloomberg.

4. It could be bigger than Twitter, which was launched 10 years ago, and not last week: on Friday, just over 3% of U.S. Android users were playing the game daily, compared to 3.5% active Twitter users. New users are installing Pokémon GO every day, which means it very likely could pass Twitter.

5. Pokémon Go is free to play, but if you want to get anywhere in the game, analysts say you’ll probably have to make some in-app purchases, according to Macquarie Capital Securities Analyst David Gibson, Bloomberg notes. These will likely be small purchases, as the game’s App Store ranking “is being driven not by big spenders but by a large number of users.”

6. It’s already starring in both real and fake news stories: There have been some real crimes linked with Pokémon Go, including a crime in Missouri, where police said a group of four armed men had used the app to lure victims to a certain spot, where they then mugged the Pokémon Go players.

In the realm of the fake, Snopes.com has been busy busting newly-sprouted myths, including a bogus news report that blamed a major traffic accident on a hapless man playing Pokémon Go; a hoax story that said a teen was stabbed after wandering into a “bad” neighborhood while playing the game; and the awful, very fake tale that 15-year-old stabbed his little brother to death for deleting his Pikachu. Shudder.

7. Nintendo is sitting pretty right now: the company’s shares are going up, adding more than $9 billion in market value, WSJ reports. The company likely won’t earn money from the game directly. Instead, it’ll profit from owning a percentage of Pokémon GO, alongside software developer Niantic.

“We presume that out of every 100 units earned at the App Store, 30 would go to Apple, 30 to Niantic, 30 to Pokémon and 10 to Nintendo,” analyst Gibson writes. “Hence, we don’t think Nintendo will earn much directly from the game. However, Nintendo will earn income from its equity-accounted income of owning 33% of Pokémon Company.”

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