How do you interpret the frequency response of a system?

Frequency response H(jw) or H(e^jw) describes how a system affects each frequency component. It has magnitude |H| (gain at each frequency) and phase angle(H) (phase shift at each frequency). Bode plots show magnitude (dB) and phase vs log frequency. For filters: Passband (|H| near 1), Stopband (|H| near 0), Cutoff frequency (typically -3dB point), and Transition band (between pass and stop). Linear phase (constant group delay) preserves waveform shape. Reading frequency response reveals filter selectivity, bandwidth, and phase distortion.