I think one way to think of it is squares and rectangles:
A square is a rectangle, but a rectangle isn't necessarily a square.
Resistance is a form of impedance, but impedance isn't necessasrily resistive.
Resistance in the same value at all frequencies, so it always "impedes" the current in the same way. Capacitors look like open circuits in DC (infinite Ohms), but they have charging times, so as you increase frequency, impedance goes down. At "infinite" frequencies, capacitors look like short circuits. Inductors are like the opposite of capacitors. They look like short circuits in DC (since they're basically coils of copper wire), but impedance rises with frequency.
So impedance as a whole is partially resistive and partially reactive, so you can express impedance as Z = R + X * j, where "Z" is impedance, "R" is resistance, "X" is reactance, and "j" is sqrt(-1), indicating the imaginary component. (Side note: we use "j" instead of "i" because "i" and "I" are used for current...too many repeated letters!) If you know the resistance, inductance, and capacitance of a given circuit, you can take the magnitud of Z at a given frequency and get Ohms for impedance.