Prototyping is the phase of a particular feature or project in which you don’t know what the client wants and/or the client doesn’t know what’s possible.

It’s important to realize that in prototyping, there is no “right” or “wrong”. A better set of terms would be “closer” and “farther” or “hot” and “cold”. This is mostly because there is no sense of correctness or completeness during the prototyping phase, simply adaption to the client’s or user’s intuition about the interface.

Since neither side truly understands the other, then the feature or project ends up becoming a means of communcation more than it is a finished product.