Art is any form of expression that communicates concepts through imagination and skill; however, what qualifies as art is often debated as much as what qualifies as good art. In addition to recorded history, sculptures and cave paintings dating back prior to understood human cultures are considered art.
Interpretation of quality in art is a separate topic from what is considered actual art. Until recent centuries, art was considered by philosophers, critics and the public to be expression created with tools, imagination, and skill. Early civilizations, such as those in Ancient Egypt, Persia, Africa, and throughout the Americas (Inca and Maya, for example) left examples of what is considered art today including statues, paintings, sculptures and architecture. However, the purposes of these pieces are unknown; indeed, pieces like those from the Maya civilization (from 1500 BC to 250 AD) may serve more as written documents of the Mayan history than as what modern civilizations call art. Many pieces could be idols to praise deities or monarchs.
Art is often classified by when it was created (the art age), its function (critical or not), advancement from previous forms (perspective painting, for example), purpose (ritualistic, story telling, propaganda) and almost any other division imaginable. There are probably as many categories of art as there are critics and there are as many critics as there are viewers of a given work. Art history is a subject to itself with thousands of courses at universities across the planet covering such diverse subjects as oral poetry traditions of the rhetorics such as Plato to modern graffiti mosaics created using chalk and recycled materials.
For contemporary cultures, art describes almost any human activity that creates a product that is not necessarily functional including painting, written or oral fiction, performances of any kind, sculpture, music and, in the most modern context, computer-based (including the internet) media. In some cases, the art is functional as well, especially in furniture and architecture. Traditional understanding of art is difficult to summarize; however, there are ways to categorize art without analyzing the subjective value of the work, beginning with the aforementioned categories. For example, art created during the Victorian era is often placed together in the category of Victorian decorative arts. Introductory books and college courses are excellent places to begin understanding styles of art, how to classify art work and how to recognize the distinctions between styles.