Vertical or horizontal lines convey a sense of stability or a static feel to an image. Horizontal lines can indicate distance and vertical lines can indicate height, balance, strength. Diagonal lines convey a more dynamic scene. Lines can be straight or curved, thick or thin 

The purest essence of a shape in a photograph is a silhouette—no form, texture, or color. Due to its high contrast with its surroundings, a silhouette is also most visually apparent. Shapes are visually defined by the intersection and/or closing of lines. 

It's the 3D aspect of the objects in your photos. Very similar to shape, form takes this element into the 3d world. Using values to make an Image no longer flat adding Depth.

Low Aperture

Texture