The foreground is the area of the picture space which is closest to the viewer. The foreground is the area which is located directly above the picture plane. (Read more after Break)
Painters use tonal changes in the painting to emphasis changes in the pictorial space, in addition objects and figures shown in the foreground are presented with a greater degree of detail in order to emphasize and add to the apparent illusion of proximity between the spectator and the figure and/or object. The further and object is away from the viewer; and the further it recedes back into the pictorial space the object will be shown in less detail.
Ideas of separate areas of space behind the picture plane, emerged when early Renaissance artists developed illusionary perspective to heighten the degree of reality and sense of naturalism within their compositions by turning a single space into three respective ares, the: foreground, middle-ground and the background.