If the leading term in a polynomial has an exponent of 2. It is also called second degree polynomial.
Example:
f(x) = 5x² + 4x - 3; the leading term is 5x² whose exponent is 2.
f(x) = (x-7)²; the leading term is x².
f(x) = 4x(x-3); the leading term is 4x²