Each camera maker seems to name these differently.
The amount of the compression settings will differ for different cameras.
What they are talking about is the amount of compression that the camera applies to .jpg photos.
The less compression, the better the photo quality.
The purpose of compression is to let you reduce the file size of each photo.
The effects of compression is dependent upon how complex the photo is. If you have a photo that has a lot of blue sky and no trees or grass, you will be unable to tell the difference between any of the compressions.
Superfine is the Highest Quality & Lowest compression.
Fine is somewhere between Superfine and Normal.
Normal is the Lowest Quality and Highest compression.
To do some testing, take a non-zoom picture that includes a lot of trees that are from 50 to 75 feet away. Try to include grass in the photo and very little sky. The more surfaces there are, the more complex the picture will be.
Take the same picture with the setting at Superfine, Fine and Normal.
Compare the results by using some photo viewing software that will let you zoom into the picture.
You should see the tree leaves start to look blurry and muddled with the Normal setting. The Fine setting should be better and Superfine the best. Many times you may see no difference between fine and superfine.