Short answers, pulled from the story.
Composition means putting together and describes how an artist organizes visual elements within a work of art. This process applies to music, writing, photography, and painting as well as graphic design where it often becomes page layout.
Visual artists use line, shape, color, texture, value, form, and space as seven core elements to build their vocabulary. Line serves as the path that guides the eye through a piece while shape defines areas with edges whether geometric or organic forms.
Lines function as optical phenomena that direct the viewer's gaze by creating literal paths like telephone cables or power lines. Oblique lines convey movement while angular lines suggest dynamism and tension and horizontal lines found in landscape photography imply calmness and tranquility.
Positive space contains the subject of the piece itself while negative space fills the empty areas surrounding those objects. In drawing or painting this space is an illusion rather than physical reality and artists can make spaces open or closed shallow or deep depending on their goals.
The rule of thirds divides an image into nine equal parts using horizontal and vertical lines so important features should fall near these lines or their intersections. Placing subjects near one line stops them from bisecting the image equally and Salvador Dalí aimed to disrupt traditional composition and challenge viewer expectations.