what do you mean by "high impedence state(Z)"?

hi, what happens in high impedence state?
when i say that something is in high impedence state, what's its logic level will be?
thank u

it will be either 0 or 1. it may transition between the two at any time. in some cases "pull-up" or "pull-down" resistors are added (or built into the IO) to weakly force a 1 or 0 without preventing other circuits to strongly force a 1 or 0 on the net.

high impedance state means that neither 1 nor 0.... When a device output a Hi-impedance state it means that it is not being driven by the circuit, and thous has no effect on the operation of Circuit.

ok, but can metastable states be called as high impedence state?

No. Metastable is 0 or 1. Z is Z.

Usually the output impedance of a digital circuit is quite low so that it can set the line to which is connected in high or low logic state, that means high (close to Vcc or Vdd) or low voltage (close to ground). If you connect the outputs of two devices toghether, you will create a strong short circuit if one is high and the other one low state because you will connect roughly Vdd (high) and ground (low) with a low impedance in between.
If, instead one of the two outputs is put in high-Z means that its output impedance is very high than even if it is connected to the output of another device, this not in high-Z, everithing will work properly since the high-Z circuit will have no impact on the output line.
As an example, if we have two devices having 'normal' impedance of 2.5 ohms each and are supplied at a Vdd=5V, the connecting directly the two output, if one is high and the other one is low the current will be roughly (5-0)/(2.5+2.5) = 1 A !
If, instead one is in high-Z state, let say its impedance is 100 kohm then in the same situation as before, the current will be (5-0)/(100000+2.5) = 50 uA and the line will have the logic state of the device that isn't in the high-Z (three-state).

no metastable state is different because it is driven by the circuit, whatever value be there.
but the high impedance corresponds to the Value of output which is not driven by circuit, and does not effect the other output values.