Trace

Trace[expr] generates a list of all expressions used in the evaluation of expr. Trace[expr, form] includes only expressions matching form.

Examples

Trace an evaluation:

Trace[2 + 3]
(* {2 + 3, 5} *)

Trace specific operations:

Trace[Factorial[5], Factorial]
(* {{Factorial[5], 5 Factorial[4], ...}} *)

Trace a function call:

f[x_] := x^2 + 1;
Trace[f[3]]

Please visit the official Wolfram Language Reference for more details.