The Principles of Gestalt are a set of perceptual laws that are used in design and advertising to create effective and attractive visual compositions. The three principles you mentioned - symmetry, closure, and proximity - are some of the most important.

Symmetry refers to the equality of elements on both sides of a central axis. Symmetry can be used in advertising to create visual balance and harmony in a design.

The principle of closure refers to our mind's tendency to complete incomplete patterns or fragmented shapes. In advertising, the use of incomplete shapes and patterns can be effective in attracting the viewer's attention and creating interest.