Physical Texture is the texture you can actually feel with your hand. The build up of paint, slipperiness of soft pastel, layering of collage - all the things that change the nature of the papers surface. Visual Texture is the illusion of physical texture, created with the materials you use. Paint can be manipulated to give the impression of texture, while the paper surface remains smooth and flat. Traditional transparent watercolour makes little use of physical texture other than the roughness of the paper.
Mixed media allows advantage to be taken of physical as well as visual texture.
This detail shows the use of visual texture. The surface appears fractured and broken but this is an illusion created with the paint. The paper in this area of the work is smooth and flat. In this detail patches of Japanese rice paper, gesso and thick swipes of soft pastel add a strong three dimensional physical texture. Understanding the difference between physical and visual texture helps us take full advantage of this element.