Astronomy is the scientific study of the planets, stars, galaxies and the universe. An astronomer is an individual who has an educational background and profession that relates to astronomy. There are many branches or specialties in the field of astronomy.
An amateur astronomer is an individual who studies astronomy as a hobby. There are thousands of amateur astronomer all over the earth. Some are casual and devote a few hours a year to the subject. Others devote many hours a week to their hobby.
Amateur astronomers have contributed significantly to the field. In fact, according to NASA, Amateur astronomers watching coronagraph movies on the web are responsible for
nearly all of the new finds of comets near the Sun in SOHO images this year. Imagine discovering a major commit and having it named after you. This happened to Alan Hale and Tom Bopp when they both discovered a comet that you may know as Hale-Bopp!