These nouns that name people: woman, grandfather, instructor, cook, scientist, participant, and so on.
These are nouns that name places: city, country, kitchen, bathroom, river, lake, school, church, hospital, and so on.
These are nouns that name things: chair, flower, mouse, pencil, photograph, pie, and so on.
These are nouns that name ideas or abstract concepts: comfort, energy, success, kindness, friendship, love, peace, hatred, and so on.
Common nouns identify objects in general. When you say “the president of the United States,” the word “president” is a common noun. Although it may refer to a particular president, the word itself does not identify a president in particular.
When you say “the beach was crowed,” the word “beach” is a common noun. The word itself does not identify a specific beach.