The new Sony a7R III has a new function called Pixel Shift. This function basically increases the resolution of your images by 4 times. In short: the camera takes 4 photos and shifts the sensor 1 pixel in between. By combining these images later (the camera itself doesn’t do this) you get an image that has 4 times the resolution of a normal raw image (4 x 42 megapixel).
This does NOT mean your file is suddenly 168 Megapixels. The files you get are still 42 megapixels but they contain way more detail, especially noticeable when you zoom in 100%.