For questions about the frequency response of electrical circuits. Also consider using the related "bode-plot" and/or "nyquist-plot" tag if your question involves a Bode and/or Nyquist plot, and/or the "stability" tag if your question is about the stability of an electrical circuit.
The response of an electrical circuit (both magnitude and phase) to an input as a function of frequency, often plotted as a Bode or Nyquist plot.