Yes, PNG is typically lossless, but it’s a raster format (like GIF or BMP) that is somewhat tied to the resolution of the display device. PNG also has different bit depths (meaning the number of bits per color per pixel).

To simplify a bit, raw format typically saves everything in the form it came off the sensor, plus all the settings currently active, so all of the data on the sensor is saved, so lots more latitude if you need to modify the photo in PP.

There are some things that are unfixable, like a blown color channel (overexposure).