People in society who make well above-average incomes that can afford a comfortable lifestyle. The upper-middle-class tend to be well educated and have a lot of work autonomy in whatever they do for a living. Most upper-middle-class tend to live in more upscale neighborhoods that are too expensive for their counterparts, the middle-class. Therefore, the middle-class and lower classes too, tend to look up to the upper-middle-class and follow in their footsteps.
Take a stroll through Whole Foods on a weekend, you're bound to see many people apart of the upper-middle-class.