It's just that fabric is about half appearance and half feel, and even the look is different in person than when on screen.
Before I get too far: I really have to know fabric better all the time. I sell vintage clothing, and my buyers and I want to know what a thing is made from. To know this is to tell someone whether she will be allergic, how to wash or clean the item, predict dye-ability. It is to know how fine it is, how long it will last, how the color will hold up. It helps make certain the vintage. It gives a better sense of how it will feel when worn. Buying clothing online is hard enough, and knowing all you can about the item is just smart.
Let me start with one colossal resource in the form of a heavy-duty dictionary, Fairchild's Dictionary of Textiles 7th Edition, Phyllis G. Tortora, editor, Robert S. Merkel, consulting editor, Fairchild Publications New York, 1996.
This thick volume, which runs about $47.00 new and not much less used (there are previous editions, which I've not seen, for less than half used) is a necessary compendium. There is so much more to each textile defined than expected, and often I get stuck reading and reading. Today it was muslin, and here is the whole definition to give you an idea of the depth of this book: