Besides senses that connect us with the external world, we also have sensors in our body. Cold feet, stomach aches, headaches can be the source of displeasure. However, feeling your muscles during exercise can be a source of pleasure. Sensual pleasures are one group of pleasures. They can be further divided into internally or externally caused pleasures, and these can be further divided into the particular sense organs.
Emotions are another group of pleasures and displeasures.
Many emotion theorists agree nowadays that emotions are caused by believe-desire comparisons or appraisals. The comparison between beliefs and desires explains why people often react differently to the same event. Two students might get a B in a class. One student might be overjoyed, the other totally depressed. We can infer from these different emotional reactions that the two students desired different grades.