Your natal horoscope (Birth Chart) is the map, an outline of sorts, of your personal energy at the moment of your birth. How you fill it in is up to you. Nothing is fated.
It is based on the date, exact time, and location of your birth, showing where the planets were at that precise time and how those planetary energies exemplify who and how you are. It sets the template for how you receive and react to the ever-changing energies of the universe.
The unique blending of all of your planetary combinations and your unique soul is what gives you the story of you. Each of us is an individual with so much more to investigate than just our Sun Sign, which is the core of our identity and ego needs. We are also our Moon Sign, our emotional response and makeup, our instinctive subconscious. We are our Ascendant (Rising Sign), the face/personality that we show the outside world and that can hide much of what goes on inside of us. The synthesis of this with all of the other planetary positions makes up the individual you.