ExpandAll

ExpandAll[expr] expands out all products and integer powers in any part of expr.

ExpandAll[expr, patt] avoids expanding parts of expr that do not contain terms matching the pattern patt.

Examples

ExpandAll[(1 + x)^2 (1 + y)^2]
(* 1 + 2 x + x^2 + 2 y + 4 x y + 2 x^2 y + y^2 + 2 x y^2 + x^2 y^2 *)

ExpandAll[(a + b)^2 / (c + d)^2]
(* (a^2 + 2 a b + b^2)/(c^2 + 2 c d + d^2) *)

Please visit the official Wolfram Language Reference for more details.