The world of art is often broken down into classifications for the purpose of easy identification. All of these classifications, and there are many, make it easier for people to identify. Some are associated with a group of people such as Old Masters. This type of art consisted mostly of paintings that were created by a group of European artists. Many of the artists actually created their works in other mediums, but only their paintings count when speaking of this group.
The time when a group of art began to be created is also part of art classification. Many people have heard of primitive art, and they often associate it with ancient relics. This is not quite true as modern artists continue to create primitive art. The category of modern art sounds as if it is being created today. Some of it is, but it actually began in the 1800's. All of these categories are simply specific ways to ensure people are talking about the same type of creations.