Several days alone in wild country, fasting, without a tent or a book, inside a structured programme of preparation and return. Old, thoroughly tested, and the closest thing here to a rite of passage rather than an experience.
The structure is what makes it work and what distinguishes it from camping. Several days of preparation with a group and guides, during which you articulate what you are actually there for. Then three or four days and nights alone within an agreed area, fasting, with a daily stone-pile check so the guides know you are alive. Then several days of return, where each person tells the story of their time and the guides mirror it back.
The solo itself is mostly boredom, cold, hunger and time. What people report as significant almost always arrives in the last day, or in the telling afterwards.
On the name: the schools listed here are transparent that they teach a Western form, drawing on cross-cultural rites of passage rather than claiming authority over any nation's ceremony. Anyone selling you a vision quest with borrowed regalia and no such acknowledgement is doing something else.
A representative shape drawn from how these are typically run. Use it as something to ask against, not as any one centre's timetable.