Here's a breakdown:
* They are not inherently different from common nouns: They are simply a specific kind of noun.
* They are distinguished by their capitalization**: This is the most obvious way to recognize a proper noun.
* They are unique to a particular person, place, thing, or concept: This is the key characteristic. For example:
* People: "Jane", "Albert Einstein"
* Places: "Paris", "Mount Everest"
* Organizations: "The United Nations", "Google"
* Things: "The Eiffel Tower", "The Mona Lisa"
So, while proper nouns aren't "made from" anything, they are distinguished by their specific referent and their capitalization.