Boondocking refers to camping on land without a developed campground, generally on BLM (Bureau of Land Management) land. Boondocking sites are generally first-come-first-serve and do not contain any accomodations. With a few exceptions, it's almost always free to camp on BLM land, but there are a few rules that it's important to adhere to. Check out this page on blm.gov for a complete list of rules and regulations.