quote

;; ' is the shortcut for quote
user> (= 'a (quote a))
true

;; quoting keeps something from being evaluated
user> (quote (println "foo"))
(println "foo")

=> *clojure-version*
{:major 1, :minor 5, :incremental 0, :qualifier "RC17"}
=> (quote)
nil
=> (quote 1)
1
=> (quote 1 2 3 4 5) ; this worked in Clojure 1.0 through 1.7 but stopped working in 1.8
1
=> quote
CompilerException java.lang.RuntimeException: Unable to resolve symbol: quote in this context, compiling:(NO_SOURCE_PATH:1:42)

;; Proof that ' is just a syntactic sugar for quote:
user=> (macroexpand ''(1 2 3))
(quote (1 2 3))

;; Two ' must be used because reader processes and removes the first one

;; Quote returns the argument you pass it, without evaluation. So:
;; In the expression `(quote 42)` the argument is the number 42 and...
user> (= (quote 42) 42)
true         ;; ... it is returned without any evaluation and...
user> (= (type (quote 42)) (type 42) java.lang.Long)
true         ;; ... as expected, without changing it's type.

;; In the expression `(quote (quote 42))` the argument is the list of two
;; elements `(quote 42)` ...
user> (= (quote (quote 42)) (list (read-string "quote") (read-string "42")))
true         ;; ... and it is returned without any evaluation and...
user> (= (type (quote (quote 42))) (type (list "1st-elem" "2nd-elem"))
         clojure.lang.PersistentList)
true         ;; ... again, without changing it's type.

;; Since clojure 1.9, if all keys in a map have the same namespace qualifier
;; then the common namespace become the prefix of the map.
user> 'org.clojure/clojure
org.clojure/clojure

user> '{org.clojure/clojure 3}
#:org.clojure{clojure 3}        ;; expecting {org.clojure/clojure 3} but not

user> '{org.clojure/clojure 3 :k 8}
{org.clojure/clojure 3, :k 8}   ;; Because of the keys' different namespaces  

;; If you want to avoid second case then flip *print-namespace-maps* temporally.
user> (binding [*print-namespace-maps* false]
        (pprint '{org.clojure/clojure 3}))
{org.clojure/clojure 3}
nil

;; 'This is not a thing about quote. It is about map with key of namespaced keyword.'
;; (@ShiTianshu's reply is quoted from below link)
;; To know the detail reason, go to the below link and see the reply of @didibus.
;; https://clojureverse.org/t/the-quote-special-form-behaves-strangely-on-maps/4879#post_2