* Common nouns refer to general, non-specific things. They are not capitalized unless they begin a sentence.
* Proper nouns refer to specific people, places, or things, and are always capitalized.
Here's an example:
* Common noun: I lost my ring.
* Proper noun: The Queen wore a diamond ring.
In the first example, "ring" is a general term referring to any ring. In the second example, "Queen" refers to a specific person (Queen Elizabeth II), and "diamond ring" likely refers to a specific ring owned by the Queen.