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Clojure has four core collection types — all immutable:

Vector [1 2 3] — indexed, fast random access. Use this most of the time.

(def v [10 20 30 40])
(get v 0)         ; 10
(v 0)             ; 10  (vectors are functions of their index!)
(conj v 50)       ; [10 20 30 40 50]  (append)
(count v)         ; 4

List (quote (1 2 3)) or '(1 2 3) — singly linked, fast prepend. Less common than vectors.

(def lst '(1 2 3))
(first lst)       ; 1
(rest lst)        ; (2 3)
(cons 0 lst)      ; (0 1 2 3)

Map {:key value ...} — unordered key-value:

(def person {:name "Ada" :age 36})
(get person :name)        ; "Ada"
(person :name)            ; "Ada"  (maps are functions of their keys)
(:name person)            ; "Ada"  (keywords are functions too!)
(assoc person :role :ceo) ; new map with added key
(dissoc person :age)      ; new map without :age

Set #{1 2 3} — unique elements:

(def s #{:a :b :c})
(contains? s :a)  ; true
(conj s :d)       ; #{:a :b :c :d}

All operations return new collections — never mutate.