Apparent power in an AC circuit is the resultant of the active and reactive powers. In complex number, S = P + j Q. Where the S is the apparent power, P is active power and the Q is reactive power.
Active Power or True power, S = V x I CosΦ W, Current and Voltage in phase.
Reactive Power, Q = V x I SinΦ var, Current and Voltage 90° out of phase.
Apparent Power, P = V x I VA