Overexposure occurs when too much light reaches the camera's sensor, resulting in a loss of detail in the highlights of an image. This can lead to areas of the photo appearing white and lacking detail. Overexposure can be corrected by adjusting the camera settings such as aperture, shutter speed, or ISO. In post-processing, overexposed areas can sometimes be recovered to an extent, but it's generally best to avoid overexposure in the first place to preserve image quality.