They can mean a movement along the demand graph, as price changes. Or, they can mean a shift of the whole demand graph. Here are some situations where someone might say the demand changed. As the AIDS epidemic spread, sales of rubber gloves skyrocketed. A wellness clinic hires a handsome receptionist.
More patients come.
You cut your price on physical examinations. More patients come. The Federal government releases a report saying that your hospital has death rates that are significantly higher than average. Patients go elsewhere. You extend your operating hours.