The day before a student graduates. The first day of a new job. A student with a stack of bills who doesn't have enough money to pay off. Each of the people described above is suffering from stress. Stress is composed of stressors and stress responses.
Stressors cause stress.
In contrast, stress responses are the mental and physical ways in which you react to a stressor. Stress exists at many levels, each with its own effects. Everyone has their own way of dealing with stress. The effects of stress can be temporary or long term. Since no one can avoid stress completely, you must learn how to manage it.