Hi there!
Copyright laws are laws set in place to protect the author of an original work from plagiarism, piracy, and unauthorized republication. Anyone who breaks these laws is punished with a fine and are commanded to promptly remove the copyrighted material from the market. An author protected under these laws are allowed to sell their copyright or give permission to those who ask it to use or sell their protected material. Something that is stated as a public domain is not copyrighted and can be used freely by anyone without permission, but the sell of public domain material is still illegal without permission.
-ASIAX Frequent Answerer