The Tanya (תניא) is an early work of Hasidic philosophy, by Rabbi Shneur Zalman of Liadi, the founder of Chabad Hasidism, first published in 1797. Its formal title is Likkutei Amarim (ליקוטי אמרים, Hebrew, “collection of statements”), but is more commonly known by its opening word, Tanya, which means “it was taught in a beraita“. It is composed of five sections that define Hasidic mystical psychology and theology as a handbook for daily spiritual life in Jewish observance.
The Tanya deals with Jewish spirituality, psychology and theology from the point of view of Hasidic philosophy and its inner explanations of Kabbalah (Jewish mysticism). It offers advice for each individual on how to serve G-d in their daily life.
Credit to Wikipedia for source material