Maybe you've seen the name, maybe they're a complete mystery to you, but one thing is for certain: 5 Seconds of Summer are here, and they're huge.

Feel a little behind the curve? No sweat, it's never too late to get into our handy guide, your exclusive map to navigating the boys from down under's world. Here's what you need to know, now:

1. They're Australian. That's right, folks. Like One Direction, these guys aren't from America ... so they have adorable accents. 

2. They're super young. Younger than Justin Bieber and 1D. Frontman Luke Hemmings is 19, guitarist Michael Clifford is 19, bassist Calum Hood is 19 and drummer Ashton Irwin is 21.

3. They're not a boy band...sort of. 5SOS refer to themselves as a rock band, because, well, they're a rock band! They each play an instrument and write their own songs. They've collaborated with Busted, McFly and Kaiser Chiefs, and have recently been seen in studio with Good Charlotte's Madden Brothers, Sum 41, Simple Plan, Katy Perry/Kesha songwriter Bonnie McKee and more. But considering them a boy band? That's a point of contention: Pop-punk purists often write them off for their fashion choices and famous friends, while boy band–obsessed girls often aren't familiar with 5SOS' '90s influences. Can they be both? Somewhere in between? Maybe Paramore's Hayley Williams has the answer...

4. They met at school. The band started in 2011 when Hemmings started posting cover videos on YouTube. The others joined after meeting at Norwest Christian College in Sydney, and the rest is history.

5. In the beginning, they weren't perceived well back home in Australia. Teenage pop-punk bands aren't very common in their native Sydney, where underground, alternative music is normally singer/songwriter stuff or metal and metalcore a la Bullet For My Valentine.

6. Most of them are tattooed. Yes, ladies, your new bad boy obsession is here! Luke Hemmings might be the only angel in the crew but it's only a matter of time before that changes, am I right?

7. They're obsessed with late '90s/mid-aughts pop-punk. The guys cite All Time Low, Green Day, Boys Like Girls and Blink-182 as major influences...and have you seen who they're writing with for album two? 

8. Luke Hemmings is the Harry Styles of the group. Unsurprisingly, the lead singer is everyone's favorite. He's also the youngest, the same age as most of his fans.

9. They all have distinct personalities. Michael is the loud, crazy, punk one. Calum is reserved and sweet (and a surprising party animal), Ashton is the talkative drummer and often second-place heartthrob, coming up on Luke, the de facto frontman.

10. Drummer Ashton Irwin is the best musician in the group. His father was a drummer as well, playing in Led Zeppelin and Lynyrd Skynyrd cover bands. Irwin used to cut swim practice to play in his first two bands, Swallow the Goldfish and Stuck in Reverse. He was also the last to join the band, and when he did, he made them practice six times a week. Dedication!

11. 1D's Niall Horan is credited with discovering them. The young singer found the boys' covers on YouTube, and the connection between the two groups was undeniable. Later, Louis Tomlinson tweeted, "Been a fan of this band for a while, everyone get behind them" with a link to the video for "Gotta Get Out." 5SOS now share management with 1D.

12. They weren't One Direction fans in the beginning. When they were first asked to open the U.K., U.S. and Australian legs of the Take Me Hour Tour, Luke said no, Calum was less hesitant and Michael wanted to hold out and try and score a spot on the 2013 Warped Tour. Ashton was on board, though!

13. In 2014, they wrote the song of summer. No pun intended? It's called "She Looks So Perfect." It's a sunny pop-punk number with a chorus of "She looks so perfect standing there / In my American Apparel underwear." The video is something of a treat too: the band get people of all shapes and sizes to disrobe in public places while they remain clothed. A bit of a Jimmy Eat World "The Middle" moment? Or Blink-182's "What's My Age Again?" The track even caught the attention of Ed Sheeran, who covered the song.

14. But they also write ballads. "Amnesia" is the band's second single from their debut album, and it's more 1D than straightforward pop-punk. No "hey hey hey" choruses here.

15. They hope someone starts an all-girl version of their band. Get on it, ladies!

16. Their follow-up tracks have been just as great! There's the ultra-catchy, Blink-182-meets-One-Direction second single "Don't Stop," soccer season's perfect pop anthem "Hearts Upon Our Sleeve," their flawless cover of Green Day's "American Idiot," and the naughty hit "Good Girls." Their last single was a cover of the Romantics' classic "What I Like About You," and while we wait for a second album, they've started performing a new jam, "Permanent Vacation," live.

17. Did we mention that they're, like, already massive? The boys only have three EPs out and they've already charted in their native Australia, as well as New Zealand, Malaysia, Spain, Brazil and Argentina. The She Looks So Perfect EP hit No. 1 in the UK and No. 1 in the U.S. after previously trailing behind the ineffable Frozen soundtrack. Their first album, 5 Seconds of Summer, went No. 1 stateside (they bumped "Weird Al" from the top spot!) and in twelve other countries. Their sophomore release is scheduled to drop this fall and it's only a matter of time before these guys are totally unavoidable.

18. The band's first record features amazing collaborations. Alex Gaskarth of All Time Low, Goldfinger frontman John Feldmann and Good Charlotte are involved, just to name a few friends and conspirators.

19. 5 Seconds fans call the band "5SOS," pronounced "5-Sauce." And the fandom is simply called "5SOSFam." Fingers crossed "Summer Stans" takes over some day...

20. They have their own record label. It's called Hi or Hey Records, and it's the reason the incredible Pizza cassette exists. Their first signing is Hey Violet (formerly Cherry Bomb) a Los Angeles-based band that's soon to embark on a summer tour with the guys.

21. They toured with One Direction last summer and the summer before that. We can't stress just how close these guys are! Maybe too close—Harry Styles once "pranked" the boys by running into their tour bus completely nude and knocking stuff over. While they pride themselves on being bratty punk kids, don't expect to hear any cursing on the tour. "We just don't ever say f*ck onstage," Ashton told Billboard. Luke Hemmings agrees adding, "At our own show we talk a lot of sh-t." Respecting 1D's audience? Swoon city.

22. This year they've embarked on their first ever headlining arena tour. That's right! Europe and Australia was in the Spring, their North American dates start in mid-July. Dates here.

23. They're already working on their second full-length. Yeehaw! They shared the information via Twitter Tuesday night, August 19, writing "Off to write some more with John and Roy! Wanna make this second album epic for you guys :)" We can't wait! In fact, we're already documenting every detail. Click here for the 411.

Do you think you already know 5SOS? Take our quiz and find out!