A proper fraction has a numerator that is smaller than the denominator. An improper fraction has a numerator that is larger than the denominator. A mixed number has one whole number sitting next to another fraction, which may be either improper or proper.
For this fraction, 7 is the numerator and 3 is the denominator.
7 > 3
There is no external whole number.
7/3 is an improper fraction.
Hope that helped =)