@filmfann is correct. I consider myself to be one, but only recently labelled myself as one, because I’d never heard of the term until well into adulthood. That said, I absolutely identify with the definition of the term and it’s how I’ve been my entire life.
I would say that, yes, it can absolutely have bearing on your life and relationships. Growing up, I never understood why people made such a big deal about the fact that I wouldn’t sleep with people until an emotional attachment/connection had been made. I used to get mad at people for asking me what I considered to be stupid questions. “So… why don’t you sleep with people? I don’t get it”. At the time, all I knew how to counter with was, “I don’t know. Why do you?! I’m just not into meaningless sex.” No one got it, and until very, very recently, I didn’t realize how much of a minority I was when it came to sex. It can also determine how many people are willing to date you, because if you don’t put out by a “reasonable” (by most of society’s definition) amount of time, a lot of people aren’t willing to give you much of a chance.
People also confuse making the choice to wait to engage in sex before marriage with someone who identifies as being demisexual. The difference in that case is that A) those who wait for marriage are making the choice – usually for personal moral or religious reasons, and B) most people who wait for marriage are still able to feel sexually attracted to someone without the need for an emotional connection. For a demisexual, the desire is simply non-existent until a genuine emotional connection has been established.