For those you don't know, many have speculated "Fine Line," which is loaded with lyrical breakup material, is about Styles' breakup from his ex-girlfriend, Camille Rowe. The singer even put one of her voicemails on his song, "Cherry," with her permission.
"I think I definitely write from a personal experience," Styles told Ellen. "I think a lot of people do. I think if you want your songs to be honest and connect with people, it's usually from writing honestly. So yeah, it's definitely about, I guess, what I was going through at the time. And that's both good and bad."
He continued, "I think the thing with this album for me is while I was making it, the times when I was kind of sad were probably like some of the saddest times in my life, but then at the same time the times when I was happy were some of the best times I've ever had in my life. It's both, it's a fine line."
While Ellen -- who was once photographed on a boat with Kendall and Harry in 2016 -- attempted to get Styles to reveal anything about his relationship with her, Styles clammed up as he remained tight-lipped.
"You and Kendall are really good friends now, right?" Ellen asked, as Styles replied casually, "Yeah, we've been friends for a while now, yeah, for like several years."
"It's sweet that you all are still really good friends," Ellen added, grinning.
"Yeah. Yeah, I think so. Right?" Styles answered, smiling. "OK!" he exclaimed and then grabbed a sip of water.
Also while at "Ellen," Styles participated in one of the show's hilarious hidden camera pranks, where the celeb must do and say whatever Ellen tells them to do. This time Styles pranked a pizza delivery guy and the result was absolutely priceless.