Imagine trying to describe what it feels like to experience anger or sadness to an emotionally blind person like a sophisticated robot. This robot is highly intelligent but does not experience emotional affect. Your difficulty in describing an emotional feeling illustrates:

Qualia characteristic of emotions

Explanation:

The word qualia means a quality or property or experience which can be used to form a perception of something or some identity. Here, a person is trying to describe what it feels like to experience anger or sadness to an emotionally blind person or a robot. But, in order to understand emotions, the robot will need to perceive the quality, property and the will need to perceive the experience associated with that emotion which it is not capable of. Hence, the difficulty here in describing an emotional feeling is the problem in describing the qualia characteristic of emotions.