At the core of
Mathematica is the foundational idea that everything—data, programs, formulas, graphics, documents—can be represented as symbolic expressions. And it is this unifying concept that underlies
Mathematica's symbolic programming paradigm, and makes possible much of the unique power of the
Mathematica language and system.
FullForm — the full form of an expression, without shortened syntax
expr/.rules make replacements for any occurrence of a pattern in an expression
Map,
Apply — map, apply a function at any level in any expression
Part (
..[[..]]) — numbered parts of an expression, reset using
=
Cases — find occurrences of a pattern in an expression
