What is a common noun? Definitions and examples would be helpful!

A common noun is a non-specific name for people, places. things, events.
Non-specific means it does not refer to a particular person, place, thing, or event. It can refer to anyone/anything within a class or group.
A common noun starts with a lower case letter.
Examples:
boy — can be any boy
A proper noun could be “Samuel”.
city — can be any city
A proper noun could be “New York City“.
teacher — can be any teacher
A proper noun could be “Miss Sandoval”.
cat — can be any cat
A proper noun could be “Garfield”.