What is the difference between absolute threshold and difference threshold?

The absolute threshold is the minimum amount of stimulation needed to detect a stimulus 50 percent of the time, such as the faintest sound a person can hear in a quiet room. The difference threshold, also called the just noticeable difference, is the minimum change in stimulation needed to detect a difference between two stimuli 50 percent of the time. Weber's law states that the difference threshold is a constant proportion of the original stimulus: a heavier object requires a larger change in weight to notice a difference than a lighter one.