Filter design is the process of creating systems that selectively allow certain frequencies of signals to pass while blocking others. This is crucial in various applications, such as audio processing, telecommunications, and electronics. Filters can be categorized into types like low-pass, high-pass, band-pass, and band-stop, each serving different purposes based on the desired frequency response. The design involves mathematical modeling and can utilize components like resistors, capacitors, and inductors in analog filters, or algorithms in digital filters. Tools such as MATLAB or Python libraries are often used to simulate and optimize filter performance, ensuring they meet specific requirements for signal integrity and quality.