This is selling your time in the labor market in return for income. With this type of work you usually give up some control over your time and this control is given to your employer. This is using your time to produce your own good and services. This is doing activities like laundry, washing your car, running errands, cooking meals, and studying. This is non-work use of time like watching TV, playing golf, going to a movie, taking a nap, etc.
Work is a source of disutility or dissatisfaction.
There are few people who work because the work gives them satisfaction. Most people work because the net utility is positive. Net utility is the utility of consumption made possible by working minus the disutility of the work itself. A rational consumer allocates their time so that the marginal utility of the last unit of time spent in each activity is identical. You are not even aware that you are doing this.