The public domain is defined as simply available for public use as it is not protected by copyright. Therefore, they are images, photographs or images available for any purpose, whether personal or commercial. Also note that since they are not copyrighted and no one can claim ownership, they are therefore free.
It's not just old stuff, but also the latest new work donated by generous contributors, making the public domain an always up-to-date and comprehensive resource.
Each year, bookstores sell hundreds of thousands of copies of works that are in the public domain and are simply reprinted. In fact, there are entire companies that publish almost all public domain material. Public Domain provides real, instant solutions for any project you create, and content can be downloaded in seconds and used in hundreds of different ways.
You can also build an amazing database of useful content for personal or business use, including old books, movies, photographs, maps, patent drawings, comics, and more. The supply is practically unlimited.
The public domain is a colossal, gigantic, huge, massive (get it?) treasury of writings, images, photos, music, illustrations, magazines, and other creative material that you are free to use for whatever purpose you want.
You can remix or modify public domain works and incorporate them into your own works. You can repack them. You can even reprint them, resell them in digital format, and do one of countless other things with them. For example, all of Shakespeare's plays are in the public domain and have been used in over 420 feature-length films. If the plays had just been written, they would be copyrightable, and licenses would have to be obtained before the scripts could be used.
Thought content is still king, but…