TEXTURE ranges from the smoothest polished mirror to the roughest mountain range as seen from an airplane. The term is often misused to refer only to rough surfaces but this is not correct. All surfaces have texture.
A designer recognizes that different textures can affect interest in different ways. Some surfaces are inviting and some are repellent and so are the textures that suggest those surfaces. Using different textures can increase interest in a composition by adding variety without changing color or tone/value relationships.
While texture can make an image more interesting it is not a strong enough element to be useful for organizing a composition. Tone/value and color contrasts are more efficient at that.
Visual texture appears to the eye to be a surface variation but it is in reality flat. If you run your hand over the object you will not encounter the variations found in tactile textures. The surface changes in light and dark are the result of value or hue changes and not a change in planes.
Pattern is the repeition of elements or motifs in an organized manner. The pattern is created through surface design variations and the repetition of a single or multiple motifs. Patterns can be regular or irregular. A brick wall made of identical bricks will create a regular pattern. A plaid fabric can be either regular with the lines of color repeating in mirror sequences or an irregular plaid with an uneven series of repetitions. Some patterns can mimic textures.
A choropleth map uses colors or shading to show differences between areas. Areas that share a quality are colored or shaded alike. A very simple choropleth map of the United States could be made using a single color or shading pattern to show those states that have state sales taxes, state income taxes, and both sales and income taxes, leaving blank those states that have neither sales taxes nor income taxes.
Choropleth maps can be used to show differences in quantity also. If you wanted to show the percent of people graduating from high school on a world map, you could use ten colors to represent 0 to 10%, 11 to 20%, 21 to 30%, and so on. To see an example go to http://ecedweb.unomaha.edu/lessons/feogZ.htm
Hint: When dealing with texture, remember that heavily textured items will have slow gradual changes in value unless the plane ends abruptly. In contrast reflective surfaces will have sudden changes in value, from one extreme to another, with only slight changes in the direction of the planes