Coefficient is the number before a variable and constant is the number without any variable.
e.g.: x^3 + 2x^2 + 3x + 4 = 0
the coefficient of x^2 is 2 and the constant term is 4.
constant term means a no without various unknown, like 2, 4, -7....
coefficient means the no of the unknown like, the coefficient of x in 3x is 3,
coefficient of x(square) in 4x(square) is 4