Concierge MVP — you do the work manually for the first 10-20 customers. No software. Customer doesn't know (or cares). You learn the exact workflow, pricing, and edge cases before writing code. Perfect for service-shaped problems.
Wizard of Oz MVP — software UI on the front; humans (often the founder) do the work behind. The customer experiences "the product"; you experience "an unscalable thing that's teaching me everything." Used by Stripe, Airbnb, DoorDash in their first 6 months.
Feature MVP — actual software, narrowest possible feature set. Right when the workflow is clear (you've already done concierge or Wizard of Oz), or when the value is in a specific software capability that humans can't fake.
Most founders default to Feature MVP. Most successful founders start with one of the first two.