Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They use dots to show valence electrons and lines to indicate bonds between atoms. Each line represents a pair of shared electrons, while unshared electrons are shown as dots around the atomic symbols. These structures help visualize the arrangement of atoms and predict the shape and reactivity of molecules. By following specific rules, such as the octet rule, Lewis structures provide a simple way to understand how atoms interact in chemical compounds.