Serve customers who come to the barbershop. As you progress in the game more clients will arrive and you'll have more tasks to accomplish. In the first level, there's just two chairs and you only have to wash and cut. In the final levels, there's many chairs and multiple tasks to perform, like combing, drying, etc. In the advanced levels your customers will have to wait, so give them magazines to distract them and avoid prevent them to grow impatient.
Drag and drop the person to the chair, more customers will come and you'll have more chairs to deal with various customers at the same time.