You've probably heard of Sia ... because you haven't seen her. She somewhat famously sang her summer hit "Chandelier" facing away from the camera on "The Ellen DeGeneres Show," "Late Night with Seth Meyers" and "Jimmy Kimmel Live."

So who is the mysterious blonde who's fast becoming pop's next big thing? Here are three things you need to know.

As you might have already guessed from her performances, 38-year-old Sia doesn't like to be in the spotlight. (Via Getty Images)

She also often covers her face with a paper bag for photo shoots, like in her cover for Billboard. She even deleted her face from her album cover — but all this is not because she's shy. (Via Amazon)

Even though her haunting voice has graced the radio waves on hit songs like David Guetta's "Titanium" for years now, she still says becoming a celebrity is her worst nightmare. (Via What A Music Ltd / David Guetta)

She didn't always used to hate it. Back in 2009, she appeared in her own music videos and showed her face during live performances. (Via Monkey Puzzle Records / Sia)

But she told NPR she wanted to step out of the limelight after "Titanium" hit its height and just focus on songwriting. "I thought it would be a funny joke that I'm getting away with. And it was partly, I don't want to go out and sell my soul, my body, my peace of mind."

So now Sia refuses to be photographed for promotional purposes and says she isn't going to tour anymore. When she does perform, she'll do it with her back to the audience. (Via Getty ImagesGetty Images)

Speaking of writing, Sia is behind lots of hits you know. (Via Getty Images)

She wrote Beyonce's "Pretty Hurts," Rihanna's "Diamonds," Lea Michele's "Cannonball" and Britney Spears' "Perfume."  (Via Getty Images)

That's quite the resume! After working with Sia on her latest album, Kylie Minogue told The Guardian,"We're all looking for the hit and she delivers. Working with Sia was nothing short of amazing. She's a genuine article."

And on top of her crazy busy music schedule, Sia also manages to find time to get involved in the LGBT community. (Via Getty Images)

She performed at the Democratic National Convention's annual LGBT Gala back in June and even showed her face while she sang to President Barack Obama there. (Via YouTube / Gorilla Go)

Her involvement is no coincidence. Back in August 2013, Sia herself came out on Twitter as bisexual. (Via Twitter / @Sia)

She is currently engaged to filmmaker Erik Anders Lang. (Via MTV)

He popped the question in June and shared the news on Instagram with a simple, "That's an engagement ring folks." (Via Instagram / mister_business)

Looks like Sia is really having a great year in both her personal and professional life. "1000 Forms of Fear" is available for purchase or download now.