Join

Join[list1, list2, ...] concatenates lists or other expressions that share the same head.

Examples

Join two lists:

Join[{a, b}, {c, d}]
(* {a, b, c, d} *)

Join multiple lists:

Join[{1, 2}, {3, 4}, {5, 6}]
(* {1, 2, 3, 4, 5, 6} *)

Please visit the official Wolfram Language Reference for more details.