Texture in design is used to communicate the tactile feeling of a design. Texture can communicate emotion and help to understand the nature of things. Like most design concepts texture can be both physically and virtually represented in a 2-d or 3-d space by using different combinations of lines, points and shading.
In the example from Mimi and The Wolves by Alabaster shown above you can see how different elements in the frame have different textures to add depth to the illustration and make the design more visually interesting by contrasting textures to one another to make the various elements stand out from one another.
In the second example from What It Is by Lynda Barry you can see texture being used in a similar way to give different meaning to the different elements. The dog for example, in the left of the page has an extremely different texture compared to the other elements in the frame with less texture. You could also say that the scrapbook styling that she employs, not only throughout this page but the entire book, adds texture to Lynda Barry’s design, although the paper is flat the use of this ripped paper texture makes the book feel much more complex than it actually is.