Mustafa for Google Chrome, on Dev-Channel writes,
The Gestalt principles are a series of laws that are used to explain why human beings naturally find organized patterns in objects they see around them. The goal with the principles was to explain why we group objects in some ways but not others.
There are many different principles, but here I am going to look at the ones that effect grouping, these are; proximity, similarity, common fate, continuity, closure, and prägnanz.