Words of wisdom:
Pooping and peeing are basic human functions that we all must perform. Bathroom visits are simple in a sticks and bricks house with indoor plumbing but take some planning in a camper.
The simplest approach is to stay near places where toilet facilities are available. This might be in paid campsites, a friend's driveway, 24hr stores, fast food joints, rest areas, etc.
The first thing to know is that solids and liquids must be kept seperate1).
Peeing in the van is fairly simple: pee in a bottle and dump it later. Gatorade bottles are preferred by many men because of the wide opening.
Women and transfolk may find a Go Girl or SheWee-type device helpful. Consider this amazon review:
I peed everywhere. That bush? Yep. Peed on it! That tree? Uh huh. Peed on it. Those tiny woodland creatures? Screw you, b*tches! Peed on them. I peed in the sun. I peed in the rain. I peed just for fun. I peed down a drain. I peed in the light. I peed in the dark. I peed left and right. I peed in the park…
Some female campers report success with inexpensive funnels in place of proprietary female urinals, and with pee cloths instead of toilet paper.2)
The most common poop recepticle for van use is the bucket toilet. At it's simplest, it's a bucket with some kind of liner for easy removal. The deluxe bucket toilet (~$20) has a seat/lid and may also involve sawdust or kitty litter.
Composting toilets don't have to be emptied after each use but cost many hundreds of dollars. See why the bucket is so popular?
Folks without room for a bucket can use doubled grocery or trash bags. Tie off and dispose in trash after use, as one does with baby diapers or dog poop bags. Tip: those doggy poop bags are a good way to store the tied off bags until you can get rid of them.
In the wild, where allowed, one can dig cat holes.