Representation of AC Current and Voltage by Rotating Vectors — Phasors
A phasor , angular frequency (ω), and initial phase (θ) are time-invariant. It is related to a more general concept called analytic representation which decomposes a sinusoid into the product of a complex constant and a factor that encapsulates the frequency and time dependence. The complex constant, which encapsulates amplitude and phase dependence, is known as phasor, complex amplitude, and (in older texts) sinor or even complexor .
Phasor is a vary important mathematical concept used frequently for Alternating Current(AC) circuit analysis. I will try to explain some basic properties of phasors that you studied(or did not study) in school. My main purpose is to help you build up sufficient background for the next article to be published which is about transformer vector group. But in general understanding the phasor will help you in analyzing the AC circuits more efficiently. Just little middle school maths.