Novelty is the quality of being new. Although it may be said to have an objective dimension (e.g. a new style of art coming into being, such as abstract or impressionism) it essentially exists in the subjective perceptions of intelligent, sentient beings. That is, for something to be "new", there must be a being to experience it as such. To a rock or a plant, something new occurring isn't going to be recognized as new.
Novelty also refers to something novel; that which is striking, original or unusual.
Novelty has specific meanings related to the general meaning. For a list of these specific uses; see Novelty (disambiguation).