In 1981, Professor Caves first proposed the concept of "squeezed state" and indicated that the sensitivity of laser interference gravitational wave detection can be improved using the squeezed states of a light field. For the past forty years, the squeezed states of light have been successfully used in quantum precision measurements such as gravitational wave detection, displacement measurement, and phase measurement that beat the standard quantum limit. Two-mode squeezed and multi-party entangled states prepared based on single-mode squeezed states also play an important role in quantum information processing, such as quantum computation and quantum communication. This review briefly introduces the basic concepts, preparation, and detection methods of the squeezed states of light and their application progress in quantum precision measurement, quantum communication, and quantum computing.