PaRDeS is an acronym for four senses of scripture: peshat, remez, derash and sod. The word itself means an orchard or walled garden, a Persian loanword, from the same root that gives the English "paradise", and its use as an acronym is medieval, appearing in the circle of Moses de Leon and in the Zohar late in the thirteenth century. The four modes it names were older practice; the mnemonic is what is new. It is often read back into the Talmudic story of the four sages who entered the pardes (Hagigah 14b), but that narrative is an account of mystical ascent and its dangers, not a scheme of interpretation, and the identification is anachronistic.
Peshat is the plain or contextual sense, what the words say in their setting. It is the default level of all Jewish reading, and the northern French commentators of the eleventh and twelfth centuries pressed it as a discipline, Rashi interweaving plain sense with midrash, and his grandson Rashbam pushing considerably further toward contextual reading even where it cut against accepted interpretation.
Remez, the hinted or allusive sense, is where philosophical and allegorical reading was located: Maimonides' treatment of biblical anthropomorphism, and of the Account of Creation and the Account of the Chariot as physics and metaphysics in figurative dress, belongs here.
Derash is the homiletic and midrashic sense, the mode of the rabbinic sermon and of much halakhic derivation. It is universal in rabbinic Judaism and is the source of the greater part of what the tradition actually draws from the text.
Sod is the secret or mystical sense, the province of Kabbalah, held by kabbalists to be the deepest stratum and treated with suspicion by rationalists, who denied that the text carries such a layer at all.
The scheme is commonly described as a hierarchy ascending from surface to depth, but the tradition's working practice is better described as cumulative. The maxim that "a verse does not depart from its plain sense" (Shabbat 63a) was maintained by the same authorities who allegorised most freely, and the standard position is that the levels coexist rather than displace one another. The parallel with the Christian fourfold sense, literal, allegorical, tropological, anagogical, is frequently noticed; whether either scheme influenced the other, or whether both draw on a shared late-antique exegetical culture, is debated and not resolved.