Appreciative Inquiry is based on the idea that there is a difference between various types of communication (e.g. advocacy versus inquiry) and that if we truly want to understand how something works, we need to put aside judgments of what other people are saying, and try to truly understand what they have to say.
Generally, Appreciative Inquiry is an approach, often used in group settings and in group facilitation and organizational development to help people understand the organization, or the subject in question.
Appreciative Inquiry is about the co-evolutionary search for the best in people, their organizations, and the relevant world around them. In its broadest focus, it involves systematic discovery of what gives “life” to a living system when it is most alive, most effective, and most constructively capable in economic, ecological, and human terms. AI involves, in a central way, the art and practice of asking questions that strengthen a system’s capacity to apprehend, anticipate, and heighten positive potential. It centrally involves the mobilization of inquiry through the crafting of the “unconditional positive question” often-involving hundreds or sometimes thousands of people.
For more detail and to enrich your understanding of this technique you can access more definitions and explanations of this group process here.