Sarah Michelle Gellar shares the key to her 17-year marriage to Freddie Prinze Jr. (Exclusive)

You may not know this, but there are actually two different Sarah Michelles.

There's the one that millions of people around the world know and love -- Sarah Michelle Gellar -- who starred on "Buffy the Vampire Slayer" for seven seasons, and there's the one that significantly less people know -- Sarah Prinze -- who is mother to two adorable children and has been married to Freddie Prinze Jr. for nearly two decades now.

During a recent interview with AOL for her partnership with Colgate Optic White, Gellar explained the "two different people" that she considers herself to be, and the boundaries that she has set up through social media in recent years in order to maintain those two sides of herself.

SEE ALSO: Sarah Michelle Gellar is 'petrified' of her children getting social media: Here's why

"By being able to have a life that's separate," she said of maintaining her strong marriage for so long, despite being in the public eye. "You know, I always joke that I'm Sarah Michelle Gellar today, but when I go home, I'm Sarah Prinze. They're two different people, and Sarah Prinze has a separate life."

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"I was very afraid of social media in the beginning, because I felt it was kind of intrusive and since I've realized it's actually the opposite," Gellar went on. "I can show people the little bit that I'm comfortable with, because nine out of 10 people are just fans, but I still get to have that life that's just my own, and I think that that's really important and that's why I don't overshare so that it feels special and it still feels intimate and still feels like my own."

What also helps her maintain the essential boundaries between her public and private lives is the fact that her fans -- the millions of people who follow her on Instagram and re-watch "Buffy" and so on -- respect those boundaries, giving her a rare, fully-positive experience on social media that other celebrities can only dream of having.

"I'm very lucky, and I think my fans are pretty amazing. My fans are extremely kind. I talk to other celebrities and they tell me these horror stories about what people write, and I really haven't experienced that," she explained. "I don't go in and erase negative comments -- by the way, I don't even think I know how to do that -- but I think on a whole, I've presented myself in such a transparent way and in such a ... I hate using the word 'authentic,' but it's the only word I can really use. This is who I am: I do my own social media, it's what it is, and so I really do usually just get 'thank you' more than anything else, which is the reason that you then do it. It works pretty well."

Find out more about Sarah Michelle Gellar's partnership with Colgate Optic White here.