a noun is the a name of a person , place , thing , idea .
For example:
He is Ram.
(‘Ram’ is the name of a person.)
He lives in Kanpur.
(‘Kanpur’ is the name of a place.)
He likes ice cream.
(‘Ice cream’ is the name of a thing.)
He thinks honesty is the best policy.
(‘Honesty’ and ‘policy’ are the names of ideas.)