(* Note: semicolons only suppress output *)

(* Square each element of a list *)
nums = Range[10];
squares = (#^2) & /@ nums

(* Symbolic differentiation *)
expr = Sin[x]^2 Exp[x];
D[expr, x]

(* Procedure examole *)
sumSquares[n_Integer?Positive] := Module[{total = 0, i},
  For[i = 1, i <= n, i++,
    total += i^2
  ];
  total
]

sumSquares[5]

