What is the difference between the Masters and the U.S. Open in golf?

The Masters is one of the four majors that is played every year in golf and is the only major that is played at the same course each year.  Every year the Masters is played in April at Augusta National golf course and it is the first major of the year.  The U.S. Open is another one of the golf majors and is played at a different course every year, although some courses are repeated once every 8-10 years.  The tournament is normally played in the summer and gives the opportunity for amateur golfers all over the U.S. to qualify and play with the professionals.