Charlize Theron says Sean Penn was a surprise. The 'A Million Ways to Die in the West' star opened up to Vogue about her relationship with Penn and also her parents' marriage, which was not 'a great marriage.'

Theron also told Vogue she was "enjoying mommyhood," after adopting her son Jackson in 2012.

Theron said about dating, "I know so well what I want to fit in my life. And the simple answer to that is: Unless he can make my life better? My life is really pretty f--king good."

When Theron and Penn began seeing each other, Theron said, "A friend kind of stepped into that role, and I really didn't see it coming. Sean and I have known each other for 18 years. We were just really good friends. And it's been slow going because you are aware that you could screw that up and lose it. We had to think about it. But at the end of the day, it was somewhat effortless."

"It just kind of naturally happened, and before I knew it, I was in something that was making my life better," the 'A Million Ways to Die in the West' said to Vogue. "The people who really love me can see the effect it has had on me."

"The last time I was dating, I was 24," she said. "I was like, 'Awww, you're miserable and moody, but I'm just going to forgive that because you're so cute! Oh, you treat me so badly, but maybe that will change in five years when I have your children!' That just doesn't exist anymore."

However, don't expect Theron and Penn to head down the aisle just yet.

"I really do understand the importance and what that ceremony represents to so many people, but it's just such a personal thing," she said about marriage. "Let's put it this way: I never had the dream of the white dress. And watching other people getting married? I think it's beautiful for them, but to be quite honest, usually I'm sitting there just devastated. It's supposed to be this night of celebrating love, and all you see is a couple separated all night making sure everybody else is OK. It just looks like a lot of work. And as you get older, you start sifting through the stuff that really matters."

Theron, whose parents' tumultuous marriage ended with her mother shooting her drunk father after he attacked her, said she's big on commitment, but maybe not big on marriage.

"A lot of people want to make it about my past, my mom and dad not being in a great marriage, but I will tell you honestly: I have had a good amount of healthy therapy about it, and it really isn't about that," Theron said.

"Because I think that would kind of showcase itself more in a fear of long-term relationships, which I don't have at all. I want the long-term relationship. And I don't really know how to invest in the other thing."