These are words that are used to refer to common and non-specific things.
Examples: girl, boy, camera, computer, keyboard
These are names of people, places, organisations businesses, schools universities etc. They are always written with a capital letter, even if they are in the middle of a sentence.
Examples: London, Paris, Michael, Angela, Mercedes Benz, Honda, Oxfam, King Edward VII, Cambridge University.
These are words used to name non-physical things. These include feelings, states of mind, concepts etc.
Examples: love, hatered, ambition, cynicism, reluctance, mathematics, sociology
These are words that are used to describe groups of things.
Examples: platoon, class, band, cast
Note: Some collective nouns can only be used to refer to specific groups.
Examples: herd (of cattle), flock (of sheep), gaggle (of geese), caravan (of camels)
A singular collective noun refers to one group, but a collective noun in plural form refers to two or more groups of the same thing.
Example: herd / herds
singular: A herd of cattle is grazing in the field.
plural: Many herds of cattle can be seen while driving through farm lands.