Aliasing is a phenomenon that occurs when a signal is sampled at a rate that is insufficient to capture its changes accurately. This can lead to distortions or misrepresentations of the original signal, making it appear as if it has a different frequency. In digital audio and image processing, aliasing can create unwanted artifacts, such as jagged edges in images or strange sounds in music. To prevent aliasing, the Nyquist theorem states that a signal should be sampled at least twice its highest frequency. This ensures that the original information is preserved and accurately represented. Techniques like anti-aliasing filters are often used to remove high-frequency components before sampling, helping to maintain the integrity of the signal.