Is "summer" a common or proper noun and why?

Hint: A noun or naming word is referred to as a common noun. It is used to refer to generic items, locations, people, and animals that do not have distinct names. A common noun, unlike a proper noun, does not require a capital letter unless it is at the beginning of a phrase.

Complete answer:
Proper nouns are nouns that describe unique things, such as cities, countries, and continents: Gujarat (a city), India (a country), Asia (a continent), and so on. People's names are also proper nouns (like Robin), despite the fact that there may be more than one person in the world with the same name. Proper nouns are distinguishable in writing because they begin with a capital letter (except in German where all nouns are written with a capital letter no matter if they are proper or common)

Summer is a common noun. Because winter, spring, summer, and fall are generic common nouns, they do not require capitalization. Some people may mistake these words for proper nouns and uppercase them according to the capitalization rule.

For example “The butterfly landed on the flower”.
In the above sentence, the common noun butterfly is used. Because it hasn't been capitalised and doesn't refer to a specific person, location, day, or name, we know it's a common noun.

Similarly in the given question, we do not refer to a specific summer. It is generic in nature, therefore it is a common noun. Summer is a common noun.

Thus the word summer is a common noun.

Note: Some rules of common nouns are:
- Unless it begins a sentence, a common noun is not written with a capital letter.
- Seasons should be written in lowercase characters.
- Just because a word is essential in your phrase doesn't mean it needs to be capitalised.
- Add “the” if the specified common noun is a specific reference. For example, she enrolled in the local community college.