Answer:
In order to perceive a stimulus, that stimulus has to meet or exceed the absolute threshold; in order to detect a change in that stimulus, the stimulus has to meet or exceed the differential threshold.
Step-by-step explanation:
The absolute threshold is the minimum intensity of energy that is required to cause a sensation in a person, that is, the minimum or maximum maginitude that a stimulus must have in order to be captured. The absolute threshold defines our perceptual limits and varies depending on the individual. The differential threshold (Just Noticeable Difference, JND) refers to the minimum intensity at which a stimulus must be increased so that we notice a change in that stimulus, that is, it's the increase that is necessary in the intensity of the stimulus so that the person perceives a modification of the same.
Weber's law states that the stronger the initial stimulus, the greater is the additional intensity necessary for the second stimulus to be perceived as different.