The ones I looked at were typically 400 square feet - 40 foot long x 10 foot wide. 400 square feet was a maximum number many RV parks/resort would allow.
Park models have stairs/ladders for access to a loft area in very tall ceiling. This is extra sleeping room and/or storage.
They typically have full size appliances and are designed to be used full time.
Due to their large overall size, they are also extra heavy. The big park models are too big to be pulled with a 1 ton dually truck. Soooo, you have to hire someone to move it for you. Those guys move it with a mini semi called a totor.
Price range 60-90K for new ones is typical.
Below is Minneapolis craigslist park model RV for sale - sorted hi to low price. Look at these to get an idea how they differ from travel trailers or 5th wheels.