To me, the identity is a concept intrinsically related to the being. An
identifier is a mean to assess one’s identity. For example, I have an identity
and my identity card is something else called an identifier.
As nouns the difference between identity and identifier is that identity is
sameness, identicalness; the quality or fact of (several specified things) being
the same while identifier is someone who identifies; a person who establishes
the identity of.
The abbreviation ID often refers to identity, identification (the process of
identifying), or an identifier (that is, an instance of identification). An
identifier may be a word, number, letter, symbol, or any combination of those.
you only need to identify a thing if you do not know its “identifier”: the name,
address, label, icon, serial number, or other meaningful piece of information
that tells you what you need to know about the identity of that thing
