Prototyping is moving. It’s the meeting, the considering, and the conceptualizing, but with iterative progress in a concrete artifact. When you’re done, you’re left with something tangible — as well as experiential knowledge — rather than just a bunch of meeting notes and perceived agreement.
As an industry, we love to talk about “shipping” because it’s moving. “Just ship it and learn.” I submit to you that prototyping is shipping, just earlier and to a smaller group than the conventional understanding of “shipping” suggests. Ship early and often? I say prototype early and often. Somewhere along the spectrum of fidelity (unique to you and your context) prototyping naturally turns into “shipping”.