Many of the headliners for this year's Austin City Limits Music Festival are known commodities. Who hasn’t heard a song by Guns N’ Roses, the Cure or Mumford and Sons? But among those names in the big-type on the lineup is Billie Eilish, a 17-year-old who skyrocketed to enormous fame seemingly overnight. If you’re a parent, you probably know that; many teens are flat-out obsessed. So for anyone preparing to take their kid to see Eilish during the festival but still unsure what the big deal is, here's a guide to one of the most famous teenagers in the world.

She’s how old again?

Yes, you've heard right: The pop phenom is just 17 years old, making her the youngest headliner in the festival’s 17-year history. With a Dec. 18, 2001, birthday, Eilish would have been younger than a year old when the inaugural ACL Fest took place in September 2002. Some acts on the bill that year? Wilco, Jimmie Vaughan, Emmylou Harris, Gary Clark Jr. and Asleep at the Wheel. Those last two are also playing this year's fest; Eilish and Clark actually share a time slot.

If you’re still not feeling old enough: In April, Eilish became the first person born in the 2000s to hit No. 1 on the Billboard 200 chart, when she released her debut record, "When We All Fall Asleep, Where Do We Go?" And her first hit song, “Ocean Eyes,” earned millions of listeners when she was only 14.

I guess I should give her a listen.

Yes, I’d recommend it.

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Well, this music doesn’t sound like what I was expecting.

How so?

Is she pop? Is she goth? I don’t get it. What even is a pop star anymore?

Fair questions. It’s 2019, and nothing means anything, but also everything means everything, and no one gets that better than the youths. Eilish, who comes from the internet and also Los Angeles, often sports slime-green hair, wears baggy athletic wear that is candy-colored as often as it is funereal, used her orthodontic aligner as a prop in a Fader cover story photo shoot and says “dude,” like, a lot.

And her music certainly isn’t the high-energy pop you might expect if you’ve tuned into Top 40 radio in years past. You’ve got pulsating beats and pretty melodies, but they’re often layered with spooky moans, industrial clanks and ghostly hushed whispers. Eilish’s music is not necessarily the soundtrack to anyone having the time of their lives. It’s more about internal reflection and morbid stuff, like death.

Yet, the music has struck one heck of a chord with her fans. She has more than 39 million Instagram followers, and the music video for her biggest single, “Bad Guy,” which dropped in March, has racked up around 557 million views so far. It features her mugging for the camera, having suburban toy car races, prodding at men’s severed heads floating in bags and sitting cross-legged atop a muscular fellow doing pushups. Normal teen stuff.

So what is it about her that fans love so much?

Eilish isn’t like most traditional female pop stars, and that’s what makes her relatable. She comes across as pretty odd, allowing young people to express their own odd parts (and we all have those parts). Eilish has even spoken in multiple interviews of her own voracious fandom for Justin Bieber when she was younger — a level of adoration that her audience now showers on her.

Moreover, she’s a fashion icon of a different kind. You might not be used to seeing a pop star wear exaggerated, oversized clothes and sneakers with ankle-high sports socks during every public appearance, from live shows to red carpet events. But Eilish recently explained her fashion choices with a startling wisdom in a Calvin Klein ad campaign. Aware of the risks of overexposure and unwilling sexualization, Eilish said, “I never want the world to know everything about me. … I mean, that’s why I wear big, baggy clothes. Nobody can have an opinion because they haven’t seen what’s underneath.”

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OK, that’s pretty cool. But I heard she has a song called “Xanny,” like Xanax. Should I be worried about her influence on my kid?

Quite the opposite, perhaps! Eilish’s sound and aesthetic definitely tend toward the dark and angsty, but don't jump to conclusions. She told the Guardian in March, “I have never done drugs, I’ve never got high, I’ve never smoked anything in my life.” And just check out the lyrics for “Xanny”: "I'm in their secondhand smoke/Still just drinking canned Coke/I don't need a xanny to feel better/On designated drives home/Only one who's not stoned/Don't give me a xanny now or ever.”

In that same Guardian interview, the young musician also revealed that the sentiment comes from real loss and that she has had friends die from drug overdoses.

So, do we think it’s gonna be a good show?

Oh yeah. I’m not saying that parents or anyone over the age of maybe 22 will be able to truly connect with Eilish the way her young fans do. However, the artist is almost impossibly likeable in person, her voice is strong in a live setting and her visual aesthetic is singular. Even if her music isn’t up your alley, you’ll appreciate witnessing a true snapshot of current youth culture. It’s odd, it’s new and it’s good.