A crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibrating crystal to create a precise frequency signal. Typically made from materials like quartz, these oscillators are widely used in various devices, including watches, radios, and computers, to maintain accurate time and frequency. The crystal's natural frequency of vibration is stable and can be finely tuned, making it ideal for generating consistent signals. This stability is crucial for applications that require precise timing, such as in communication systems and GPS technology, where even slight deviations can lead to significant errors.