Definition - What does Public Domain mean?
The public domain refers to a category of creative works that no longer has copyrights or patents, or never did, and can be freely used or reproduced by the members of the public. The public domain also refers to land that is owned and controlled by the government of the United States.
Justipedia explains Public Domain
Public domain works are those that are no longer covered by copyright, trademark, or patent. That means that anyone can use them. It can be a book, a piece of artwork, photos, or other things that we would consider as intellectual property of some sort. A person does not need a license or permission to use something that is part of the public domain. Public domain represents things that are not private. For example, a man who owns 10,000 acres of land in Montana may give the land to the federal government as an act of charity. Once this land belongs to the government, it is no longer private land. The government can now turn it into a park, build government buildings on it, or use it for a number of different purposes. The main point is that it now belongs to the people of the United States, as opposed to one private owner.