IxD is an acronym for “Interaction Design,” which is a broad and multidisciplinary research field that involves shaping behavior and/or experiences through the use of technology. While this definition is overly concise, it is a starting point to begin to describe what an Interaction Designer does.
For a more in-depth introduction to Interaction Design, please read this article by Jonas Löwgren, professor of interaction design at Malmö University, Sweden.
In summary, there are 5 major characteristics of interaction design including according to (Lowgren 2013) : 1) changing situations by deploying artifacts, 2) exploring possible futures, 3) framing the problem while also creating possible solutions, 4) thinking through sketching and other tangible representations, and 5) the designer addresses instrumental, technical, aesthetical and ethical aspects throughout the process of design.
Lowgren, Jonas (2013): Interaction Design – brief intro. In: Soegaard, Mads and Dam, Rikke Friis (eds.). “The Encyclopedia of Human-Computer Interaction, 2nd Ed.”. Aarhus, Denmark: The Interaction Design Foundation. Available online at http://www.interaction-design.org/encyclopedia/interaction_design.html
Another very clear and visual articulation of what Interaction Designers do is provided by Bill Verplank in the following video: