The haftarah or (in Ashkenazic pronunciation) haftoroh (alt. haphtara, Hebrew: הפטרה; "parting," "taking leave", plural haftarot or haftoros) is a series of selections from the books of Nevi'im ("Prophets") of the Hebrew Bible (Tanach) that is publicly read in synagogue as part of Jewish religious practice. The Haftarah reading follows the Torah reading on each Sabbath and on Jewish festivals and fast days. Typically, the haftarah is thematically linked to the parasha (Torah portion) that precedes it. The haftarah is sung in a chant (known as "trop" in Yiddish or "Cantillation" in English). Related blessings precede and follow the Haftarah reading.
The origin of haftarah reading is lost to history, and several theories have been proposed to explain its role in Jewish practice, suggesting it arose in response to the persecution of the Jews under Antiochus Epiphanes which preceded the Maccabean revolt, wherein Torah reading was prohibited, or that it was "instituted against the Samaritans, who denied the canonicity of the Prophets (except for Joshua), and later against the Sadducees." The Talmud mentions that a haftarah was read in the presence of Rabbi Eliezer ben Hyrcanus, who lived c.70 CE, and in the Christian New Testament several references suggest this Jewish custom was in place during that era.
Read more about Haftarah: History, Who Reads The haftarah, Haftarah Blessings and Customs, Haftarah Cantillation, Haftarot On Sabbath Afternoon, Haftarah As A B'nai Mitzvah Ritual, List of Haftarot