A proper noun or proper name is a noun representing a unique thing (such as London, Jupiter, John Hunter, or Toyota), as opposed to a common noun, which represents a class of things (for example, city, planet, person or corporation). Proper nouns are the only nouns in English which have the first letter capitalized.
In English, proper nouns are not normally preceded by an article or other limiting modifier (such as any or some), and are used to denote a particular person, place, or object without regard to any descriptive meaning the word or phrase may have (for example, a town called "Newtown" may be, but does not necessarily have to be, a new [recently built] town).
Which nouns are considered proper names depends on language. For example, names of days and months are considered proper names in English, but not in Spanish, French, Swedish, Slovenian or Finnish, where they are not capitalized.