What the Hell is Fleek and Why is Kim Kardashian Using this Word, I Must Know! [VIDEO]

Recently Kim Kardashian typed an open letter to her future self. In the Letter she mentions her family and where they are headed. She also uses the term "Fleek," and I'm trying to figure out if that's a word a 34 year-old mother should be using. Check out my video above, and Kim's video below from Glamour.com, and let me know if she should still be talking like this, or maybe it's time for her to grow up?