Public Domain fonts and typefaces are free digital software that have been released to the public with no Copyright attached. This allows the public to use the fonts however they want, without any restriction what-so-ever. Then, there is the Creative Commons Public Domain Dedication freeware license (often referred to as a "CC0" or PD license) which affords the same unrestricted use of a font or typeface, with the exception that the authoring designer maintains the Copyright as credit for his/her contribution.
Creative Commons Public Domain Dedication is really freeware because it is a retains the authoring designer's Copyright with a license, but it seems that everyone in the world is embracing this license as "Public Domain" because it allows the contributor to get credit for giving back to the world community. So, even though something that is designated as "CC0" is using a freeware license, it is considered and referred to as Public Domain because that's how it is intended to function.