The Nyquist Theorem is a fundamental principle in signal processing that states a continuous signal can be accurately reconstructed from its samples if it is sampled at least twice the highest frequency present in the signal. This minimum sampling rate is known as the Nyquist Rate. If a signal is sampled below this rate, it can lead to a phenomenon called aliasing, where different signals become indistinguishable when sampled. The theorem is crucial in various applications, including audio processing, telecommunications, and data conversion, ensuring that signals maintain their integrity during transmission and storage.