A letter is a written message from one party to another containing information. Letters guarantee the preservation of communication between both parties. They bring friends or relatives closer together, enrich professional relationships and provide a satisfying mean of self-expression. Letters contribute to the protection and conservation of literacy, which is the ability to write and read. Letters have been sent since antiquity and are mentioned in the Iliad by Homer (lived around 7th or 8th centuries B.C.). Works by both Herodotus and Thucydides, also mention letters.