Texture is a visual effect that provides a sense of surface that can be touched. Varying lighter and darker pattern areas on an object creates an illusion of physical depth. Everything has a texture. Generally we recognise two types of textures, tactile - providing actual feeling of touch, used in 3D design and visual - an illusion of the surface used in 2D design. The latter is the type we can apply in web design.
Most textures inhabit a naturalistic quality and they repeat a motif in a random way. A motif is any recurring thematic element or figure in a design. A regularly repeated motif creates a pattern. Pattern requires repetition and the more regular the repetition the stronger is the pattern.
The three shapes below have been filled with different textures. The regular repetition of the motif in the triangle makes it the strongest pattern of the three.