Parks on the Air is an international award program the encourages amateur radio operators to visit public lands and parks, and to set up portable communication stations to initiate contacts. POTA promotes emergency communications awareness and communications from state and federal lands. It originated from an ARRL sponsored program to encourage Ham Radio operators to visit and operate from every US national park in a celebration of the 110th anniversary of the founding on Yellowstone National Park.
You register at http://pota.app to get started. There is no cost to do Parks On The Air.
There are activators and hunters. The activator logs the contacts and must make at least 10 contacts to count as an activation. POTA can be done on HF SSB, FT8/FT4, VHF/UHF as long as it's simplex based.