Welcome
My family has owned both RV's and converted Vans. For us it went like this. The RV was a complete purpose built vehicle and many of these are "self contained" so that they carry everything including fresh "potable" water (in tanks) to gray water (from shower & sinks stored in the gray water tanks) and that then used to flush the toilet(s) which is then stored in "black water" sewage tanks for proper disposal when at a facility. If using full service RV Parks there will be hookup for electric, water, sewage, internet/WIFI, where there may also be coin op laundry centers. (but these places may not want converted Vans in them)
The Van Life folks (Nomads) may be a more independent sort traveling & living in converted Van's, (or other vehicles such as Short or Full Size School busses, Shuttle Vans, Ambulances, and the like) Most have the essentials for cooking, eating, sleeping, and refrigeration. (of course some have other accessories for extended stays away from conveniences) Often Nomads will have a membership to any of the Nationally Syndicated Gym's (such as Planet Fitness) where they can use the showers, restrooms, WIFI, electric to recharge electronics, watch TV & chill, and use gym equipment etc) They may use fast food places for restrooms & WIFI or any other places such as Public Libraries for free amenities. The State & National Parks may be more welcoming to Nomads especially if they are Seniors. (often Sunday evenings thru Friday mornings are low priced) There are places where RV'ers & Nomads are welcome to use the parking lot after they close until the next morning. These may include Walmart (but not in all States or Places, Lowe's, Sam's Club, Target, Cracker Barrel, Flying J/Pilot, etc) Some like to use Government Lands where Bureau of Land Management grants permissions.
Nomads who have rigs that appear like common vehicles may overnight in places some wouldn't want them in. It's called Stealth Camping used as they travel to get some hours of sleep before moving on.
Van Life seemed to start in the mid 60's with the Hippy VW Van's and young people but it has grown since. It appealed to those with
limited funds and a sense of adventure, but has expanded to the many interest other people. (remote workers, snow birds, traveling workers with Rail Roads, Maritime, or Airlines who live the Van Life when off work, Graduating Students who want to travel some to find a city where they can find employment in their field, and so on)