Bikepacking is, basically, just what it sounds like: Backpacking, but getting from Point A to Point B on a bike instead of hiking. The idea and the practice have been around at least since the invention of safety bikes (the bikes we ride today, as opposed to the old high-wheelers) in the late 1880s. But it’s had something of a resurgence lately along with off-road cycling in general.
There is no way to bike the Pony Express Trail without bikecamping. The eastern part of the trail does pass through towns, and there are restaurants and hotels along parts of that portion of the route. But my understanding is after Salt Lake City, across western Utah and through most of Nevada, there are very long stretches between settlements, as it were. One section has a 400-mile stretch without even food available to purchase along the route (unless you detour a considerable way off the Trail).
So bikecamping is a necessity if you want to ride the Trail. And, really, part of the point of the experience. After all, is it really an adventure if you spend every night in a hotel?
That being said, as of the time I’m writing this, I have never been bikepacking. I don’t even know how much I’ll like it, though I’m certain some part of me won’t. The bike will be a lot harder to ride, a lot less playful, carrying all the weight of gear and food. And it takes time to get into the practice of being comfortable in uncomfortable circumstances like riding in bad weather and sleeping on hard ground.
My plan is (was?) to set up for short one- and two-day bikecamping excursions this summer (2020) to get a feel for it, then perhaps take a few longer trips in the fall. But with the shelter in place restrictions, and the unforseeable circumstances of the foreseeable future, who knows when that will be possible.