A wavefront sensor is a device used to measure the shape of a light wavefront, which is crucial in various optical applications. It captures the distortions in the wavefront caused by imperfections in optical systems or atmospheric conditions. This information helps in correcting these distortions to improve image quality in systems like telescopes and laser communications. These sensors often utilize techniques such as interferometry or pyramid sensing to analyze the wavefront. By providing precise measurements, wavefront sensors play a vital role in adaptive optics, enhancing the performance of optical instruments in fields like astronomy and microscopy.