The Tanya is the known as the "written Torah" of Chabad Chasidus. It is written by the founder of Chabad Rabbi Shneur Zalman of Liadi and consists of five sections. The first section, known as Likutei Amarim (collected sayings) deals with man and his internal struggles, and relationship with G-d. The second section, Shaar Hayichud Vehaemuna (The portal of unity and faith), deals with creation, and the unity of G-D. The third section is known as Iggeres Hateshuva (The epistle of Teshuva). The fourth section known as Igeres Hakodesh is a collection of letters penned by the author throughout his lifetime. The final section konw as Kuntres Acharon consists of essays on various topics.