One of the most popular emerging fields today in app development is user experience (UX); basically, the study of how a user actually “feels” when using a system, app, or software.  There are several factors that go into determining user experience, including ergonomics, system performance, utility, human emotions, design, and marketing. UX professionals study and evaluate how users feel about a system or an app by looking at a variety of different factors: ease of use, perception of the value of the system, utility, and how it performs certain tasks.