Whether it's the smooth glossy surface of a bowling ball or the coarseness of a piece of sand paper, all objects have a texture. Finding ways to translate that texture in a photograph so people can "feel" the surfaces you're photographing is one of the things that makes photographs seem more real. Remember, the world is a three-dimensional place (height, width, depth) but a photograph only has two of those dimensions--you can't reach in and grab anything or feel it in a photograph (though I'm sure someone is working on that!).
The best way to accent textures in a photograph is by paying attention to the direction of the light as it strikes the surfaces of your subjects and the best light for drawing out textures is sidelight. Light coming from the side casts myriad tiny shadows across the surface of the object and gives it a three-dimensional look. I photographed this old door handle with really extreme sidelight (look at how long the shadow on the left is) and the lighting really brought out the rough-hewn surfaces of the wood and the hand-hammered metal.
Sidelight also works to bring out the textures of things like a sandy beach or a gravel parking lot in a landscape. Backlighting will do the same thing, to some degree, especially if it's late in the day and the light is scraping off the landscape from a low angle. In some situations you won't see as much texture with backlighting because some of those tiny shadows (like the ones cast by sidelighting) are hidden from the camera by other objects.
You can experiment with lighting direction and its effect on texture without much effort. Try photographing a rough-surfaced rock with the light falling on the front of it sometime and then move around the rock and shoot it so that the light coming from the side and you'll see the difference immediately.
Beautiful San Francisco
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