PUD zoning is often used by developers to allow for multiple property and zoning types within a single, larger tract of land. They'll have R-1, R-2, R-3, Local Business, Office use etc. all within the original project.
They receive approval for PUD zoning and within that defined area, they build condos, attached housing, apartments, larger custom homes, etc. in different areas of the project and they usually aren't required to apply for zoning changes within the PUD to accommodate these varying properties.
Condominium is a legal form of ownership where all of the land is generally owned by the association and individuals own "units" within the condo complex.
Fannie Mae, in their infinite wisdom, or typical lack thereof, has created their own definition of PUD that means any property tha pays mandatory association dues. This could mean simply a group of 4 or 5 homes that pays dues for shared driveway maintenance or a common lake maintenance agreement.
A "site condo" is most likely a freestanding condo (not attached to other units) and is a single unit located on condo association land.
You can also have PUD freestanding units where the land is owned by the building owner and the owners pay a monthly/quarterly fee for all exterior maintenance, very similar to and often confused with condos.
You might have to get a copy of the deed to make a determinition. I've had to make this argument with LO and underwriters on many occasions because the property owner was "certain" that they lived in a condo complex but in reality it was a PUD and they owned the land.
Fortunately, some of what I've learned in 16 successful years of selling as a Realtor and broker has helped.