Memorial Day was originally called Decoration Day
... and it commemorates US soldiers who died in service to the country. The practice of decorating soldiers' graves became widespread at the end of the Civil War and there is an interesting history to the holiday which is now celebrated as the unofficial beginning of summer with a three day weekend.
Today, we spend a day at the beach or at the pool and grill out with family and friends but take a moment to both learn more and honor those who have given their lives so that we may enjoy a fun weekend.
Learn more from wikipedia (there is an interesting tidbit about Charleston) and USMemorialDayOrg