Often we associate texture with something we can feel. Something may be rough or smooth. Consider the texture of your shoes and compare this with the texture of your jumper. Feel the surface of the wall and compare it with the asphalt. Or hold a tennis ball and compare the texture with a basketball.
However, in photography we can not feel the texture of an object or its subject. As a photographer you need to look closely at the details of the surface of the what you are photographing.
The best images to capture will have strong colour contrasts or shadows that bring out the texture. In black and white images you take into account the light and dark contrasts. As with all photography light is crucial.
The light coming from the side will highlight the shadows and create different amounts of contrast and emphasis the detail of the subject. Light from above will tend to hide the texture