cons car cdr

(cons "dog" "cat")

+------------------+-----------------+
|                  |                 |
|                  |                 |
|                  |                 |
|        X         |        X        |
|        |         |        |        |
|        |         |        |        |
|        |         |        |        |
+--------|---------+--------|--------+
         |                  |
         |                  |
         V                  V
       "dog"              "cat"

(car (cons "dog" "cat"))

"dog"

(cdr (cons "dog" "cat"))

"cat"