Texture refers to the surface quality, both simulated and actual, of artwork.
Techniques used in painting serve to show texture.
For example, the dry brush technique produces rough simulated quality and heavy application of pigment with brush or other implement produces a rough actual texture.
Texture in Fine Art
Rouault painted this painting in oil paint with heavy textures. The painting technique that emphasizes actual texture is called impasto. Such textures can be applied with a stiff brush or spread on the canvas with a painting knife.
Simulated textures occur when smooth painting surfaces appear to be textured.
Source: Elements and Principles of Design: Student Guide with Activities, published by Crystal Productions
Texture in Graphic Design
Fossil Annual Report
From cover to cover, this annual report from fossil uses texture to carry the design. Fossil, by nature, effectively relies on nostalgia to position their products. Thus the notion of old ledger paper and classic catalog art are entirely appropriate. There are at least a half dozen printed paper (actual) textures in this report. As in the pages above, upon each texture sits a wonderful collection of old toys, posters and memorabilia - each enhanced by the texture behind it. The designer who learns how to use texture to influence the mood of the design and consequently that of the reader, will have learned one reason that Fossil's design has been so successful for so many years.
See the square at the bottom to get a better view of the simulated texture on the paper, making it look aged.
Source: Design Basics for Creative Results by Bryan L. Peterson