Alas these concepts really require an understanding of complex number plane - impedance is resistance generalized to complex values, reactance is an impedance that is purely imaginary. You'll need to find out about imaginary and complex numbers I think - although the short answer is that impedance is like resistance for AC (and encodes phase information). Try looking up 'phasor' on wikipedia?
Pure reactances have a phase difference (between current and voltage) of + or - 90 degrees - corresponds to the imaginary line on complex plane. Resistance has 0 degree phase difference, negative resistance has 180 degree phase difference - corresponding to real line on complex plane. General impedance can have any phase angle and magnitude - any point on the complex plane.