What does mercury represent?

In astrology, Mercury is the ruler of Virgo and Gemini, representing the expression of one's thoughts. Everyone should know the sun constellation very well, because it corresponds to the 12 constellation we usually say. The sun sign represents a person's external image, and the moon sign represents a person's character. If mercury is enhanced on the birth chart, it represents a smart and quick-thinking person. Mercury rules people's thinking and language expression, people's nervous system, hands, back and fingers. When mercury stands out in the personal map, it brings people a tendency of instability, tension and high excitement, as well as an extremely agile and lively psychological state.