What is hell? Who is punished there?

Hell is a place of fire where sinners are punished after they die. Certain classes of people who deny religion receive eternal punishment there (Maimonides, Mishneh Torah, Teshuvah 3:5-6), but most sinners are punished there for only (up to) a year (Mishnah Eduyos 2:9; Talmud Shabbos 33a). Ask a follow-up question