H-infinity is a mathematical framework used in control theory and signal processing. It focuses on designing systems that can maintain performance and stability despite uncertainties and disturbances. The "H" refers to the Hilbert space, a concept from functional analysis, while "infinity" indicates the goal of minimizing the worst-case scenario, or the maximum error in system response. In H-infinity control, engineers create controllers that optimize performance by balancing trade-offs between sensitivity to disturbances and robustness. This approach is particularly useful in complex systems, such as aerospace and automotive applications, where reliability and precision are critical for safety and efficiency.