Extract

Extract[expr, pos] extracts the part of expr at the position specified by pos. Extract[expr, {pos1, pos2, ...}] extracts multiple parts.

Examples

Extract a part by position:

Extract[{{a, b}, {c, d}}, {2, 1}]
(* c *)

Extract multiple parts:

Extract[{a, b, c, d}, {{1}, {3}}]
(* {a, c} *)

Useful with Position:

Extract[{1, 2, 3, 2}, Position[{1, 2, 3, 2}, 2]]
(* {2, 2} *)

Please visit the official Wolfram Language Reference for more details.