Mercury is associated with travel, intellect, logic and communication skills. Mercury represents quick trips, short classes, siblings, and transportation.
Mercury, in a natal chart, is very important for understanding how you communicate with others. Mercury in Pisces may speak in visionary, poetic, and even flowing musical terms. In Libra, Mercury may be expressed indecisively or through balanced diplomatic words.
The house placement of Mercury will give you hints as to where you are likely to communicate. A 2nd house Mercury may earn her or his income through speaking. A 9th house Mercury could communicate as a teacher or publisher.
Mercury is the closest planet to the sun, is incredibly hot, and its atmosphere is constantly replenished by solar winds (unlike the Earth, which maintains its atmosphere).
And most fascinating is that a day on Mercury is twice as long as its year! Mercury rotates extremely slowly but revolves around the Sun in slightly less than 88 days.
Approximately 3 times a year, Mercury goes into retrograde, a 3-week period when Mercury looks like it's going backwards across the sky. When this happens, expect your equipment to break, you'll have misunderstandings, and travel will be exasperating.