Nouns can be divided into concrete nouns and abstract nouns.
A concrete noun describes something that we can see, hear, smell, touch or taste, such as dog, spaghetti or perfume.
An abstract noun describes something that we can't see, hear, smell, touch or taste, such as happiness, pain or love.
Concrete nouns can be divided into three smaller groups: common nouns, proper nouns and collective nouns.
Common nouns describe people, places or things, but as a general class rather than a particular individual, e.g. doctor, city, cat.
Proper nouns describe particular people, places or things, and always begin with a capital letter, e.g. Doctor Jones, Manchester, Molly.
Collective nouns are nouns that describe groups of things, e.g. flock, team, crowd.