This paragraph is quoted from Nikon, offering a good explanation of the difference:
Exclusive to Nikon cameras, the NEF is Nikon's RAW file format. RAW image files, sometimes referred to as digital negatives, contain all the image information captured by the camera's sensor, along with the image's metadata (the camera's identification and its settings, the lens used and other information). The NEF file is written to the memory card in either an uncompressed or "lossless" compressed form.
The primary benefit of writing images to the memory card in NEF format rather than TIFF or JPEG is that no in-camera processing for white balance, hue, tone and sharpening are applied to the NEF file; rather, those values are retained as instruction sets included in the file. You can change the instruction set as many times as you like without ever disturbing the original image's RAW data. Another benefit of the NEF file is that depending on the camera, it retains 12-bit or 14-bit data, resulting in an image with a far greater tonal range than an eight-bit JPEG or TIFF file.
After-capture processing of the NEF file by Nikon's Capture NX2 software, or other imaging programs, offers greater control over the final image than the processing of a JPEG or a TIFF. After processing, the NEF file can be saved as a TIFF, JPEG or again as a NEF with the addition of any applied Capture NX2 processing saved inside the file as a second or alternate instruction set. As long as the original NEF file is preserved, the "digital negative" remains untouched; processing a NEF file does not alter the original instruction set.
Source
https://www.nikonusa.com/en/learn-and-explore/a/products-and-innovation/nikon-electronic-format-nef.htmlThis one is from Olympus:
The RAW format (.orf) applies no compression and no image processing, resulting in Olympus’s own proprietary file format. Because RAW files are not compressed like JPG files, the file sizes are much larger. The trade-off is often worth it, however, since shooting in RAW offers the most control by allowing you to adjust exposure compensation, white balance, sharpness, contrast, saturation, and color space as you convert the image to a standard file format such as TIFF or JPEG.
RAW (.orf) files need to be opened in OLYMPUS Master, OLYMPUS Studio, or a supported third-party program to view and convert the image to a standard file format such as TIFF or JPEG.
Note: Images shot in the Scene modes will lose the automatic adjustments made by the camera in this mode, therefore use TIFF, SHQ or RAW+SHQ as your highest quality setting for the Scene Modes.
https://www.olympusamerica.com/crm/oneoffpages/ask_oly/crm_e_ask_oly_07_07.aspAnd this from Canon:
RAW file is the image data exactly as captured on the sensor. Any settings you apply in white balance, Picture Styles and some other areas are only appended to the image as a small header file. This means they can be changed later in RAW conversion software such as Canon’s Digital Photo Professional (supplied with the camera). A RAW file is often referred to as a ‘digital negative’ because the data can be processed and printed in different ways to produce different results – just like the negative from a film camera. Also, like a film negative, the RAW file never changes. When you open a RAW file in a software application, it is actually a copy of the data which opens. When you save this, it creates a new file on your computer. The original RAW file can then be opened again (as another copy) and worked on to produce a completely different result.
Advantages
Can be modified after capture
Maximum flexibility
Widest range of colours recorded
Disadvantages
Largest file size
Needs computer for processing
https://cpn.canon-europe.com/content/education/infobank/image_compression/file_types_raw_sraw_and_jpeg.do