Explain the concept of impedance in AC circuits comprehensively, covering its significance in electrical systems, calculation methods, practical applications across various circuit configurations, differences from resistance, complex representation using phasors, effects on circuit behavior including voltage and current phase shifts, impedance matching techniques, signal processing applications such as filtering, impedance spectroscopy, and material characterization, and its role in circuit performance analysis. Include step-by-step details, examples, and illustrations where applicable.