Identity

Identity[expr] gives expr (the identity operation).

Examples

Identity function:

Identity[5]
(* 5 *)

Identity[{a, b, c}]
(* {a, b, c} *)

Useful with Map:

Map[Identity, {1, 2, 3}]
(* {1, 2, 3} *)

Please visit the official Wolfram Language Reference for more details.