What (in simple words) is the difference between setting bind (LET) and characters (= variables) in common lisp?
Symbols and variables are two very different types of entities. A symbol is the name of something; variable is the container for the value. A variable may be called a symbol.
Binding is the association between a character and a variable; when the binding is valid, you can refer to a variable by its name. The form letcreates such a binding.
let
( ((a 1))) a 1 , , , , ( undefined). , , , let.
(setf a 1) a 1 , a ( defparameter, defvariable let), a , .
, , lisp chops, .