A generic noun is a symbol for whole group of people, places, or things in general. It represents any and all members of a group.
- A dog is a loyal companion implies any dog is a loyal companion.
- Dogs are loyal companions imply all dogs are loyal companions.
- Do you like tea?
In the above sentence the word tea is a generic noun. It is a symbol for tea in general. It doesn't refers to real tea that you can drink, smell or taste.
A concrete noun refers to a real and concrete person, place, or thing.
- The tea is strong implies the tea that I am drinking right now is strong.
- You look exhausted. Would you like some tea? In this sentence the tea is the real tea that you would like to drink.
