AC currents is the alternating current, which means that it is not constant. Usually by AC current people mean the current, which is generated by voltage with sinusoidal time dependence. For example,
where is the amplitude and is the angular frequency.
The time-dependent voltage produces the time-dependent current, which produces time-dependent magnetic field. The time-dependent magnetic field is closely related to the effect of magnetic induction and Faraday's law.
Below you can find animations of different concepts related to AC current, AC circuit, and magnetic induction.