WolframLang: Global Variable

Set[x, y]

(short syntax: x=y)

Eval right-hand-side and assign it to left-hand-side. Effectively, this is how you create a global variable. Set

Technically, Set creates a syntax transformation rule. When the pattern on left-hand-side occur, replace it by right-hand-side. [see Set and SetDelayed]

(* global variable, of current session  *)
x = 2

Clear

Clear the value of Symbols. Clear

Clear[x]

(* clear multiple variables *)
Clear[x1,x2]

(* clear all variable starting with x *)
Clear["x*"]

Remove

Remove Symbols from the system. Note: this is more advanced. Usually you just need Clear. Remove