Your element is part of your Astrological chart. The sun sign you were born in will dictate what your Element is.
Fire Signs - Aries, Leo, Sagittarius
Water Signs - Cancer, Scorpio, Pisces
Earth Signs - Taurus, Virgo, Capricorn
Air Signs - Gemini, Libra, Aquarius
Each element has a behavior pattern that it describes. It is a personality description.
Fire - People with a strong emphasis of the fire element are spontaneous and impulsive, they apply their energies wholeheartedly. Their emotional response is quick and they have a lively imagination.
Air - Airy people are quick and animated. They apply their energies in very diverse ways. They tend to intellectualize their feelings and expectations.
Water - People with a strongly emphasized water element are feeling types and are very sensitive. Their imaginative and emotional lives are deep and rich.
Earth - Earthy people react quietly and slowly. They apply themselves with endurance. Emotionally they are deeply rooted and slow to change.
This does not indicate what type of magic you can do and often has little bearing on magic in any way. We are made up of all the elements. We can use any one of them or any combination of them. Your element does not dictate what you can do, it only states a few things about your personality that, as a magic user, you might want to be aware of.