A crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a precise frequency. It is commonly used in electronic devices such as computers, televisions, and radios to provide accurate timing for various functions. An oscillator, on the other hand, is a general term for any electronic circuit that generates a periodic waveform. It can be based on various components such as resistors, capacitors, and inductors. A resonator is a passive two-terminal electrical component that stores and releases energy in the form of oscillating electromagnetic fields. It is used in electronic circuits to create and control specific frequencies.