To publish is to make content available to the general public. While specific use of the term may vary among countries, it is usually applied to text, images, or other audio-visual content, including paper (newspapers, magazines, catalogs, etc.). The word publication means the act of publishing, and also refers to any printed copies.
"Publication" is a technical term in legal contexts and especially important in copyright legislation. An author of a work generally is the initial owner of the copyright on the work. One of the copyrights granted to the author of a work is the exclusive right to publish the work.