2.3.12 Hash Table Type

A hash table is a very fast kind of lookup table, somewhat like an alist in that it maps keys to corresponding values, but much faster. Hash tables are a new feature in Emacs 21; they have no read syntax, and print using hash notation. See section 7. Hash Tables.

(make-hash-table) => #<hash-table 'eql nil 0/65 0x83af980>