Temurah is the genus and not one table: any systematic substitution of one letter for another, of which atbash, albam, achbi and ayak-bachar are species, and avgad (each letter for its neighbour, tav wrapping to aleph) is the simplest. Worked: avgad sends שלום to תמזנ.
The tradition counts temurah among the middot by which the Torah is expounded and treats it as the complement of gematria: gematria asks what a word is worth, temurah asks what it would be if its letters were changed. The Kabbalists use the substitutions to generate the permutations out of which, in their account, the world was engraved — the same pairs that Sefer Yetzirah calls the gates.
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