A "choke coil" or "choking coil" is an electrical coil of large inductance and small resistance used within an AC circuit to throttle, impede or change the phase of the current. It is also called a "reactor" or "reactance coil" in the field of engineering.
According to Murata, common mode choke coils are a type of noise filter and use conduction modes, instead of differences in frequency, to separate noise from signals. Common mode choke coils consist of two conducting wires wrapped around a single core in opposite directions, equipped with four terminals. Differential mode currents that flow through a choke coil generate flux in opposite directions, canceling each other out.