Today is a federal (national) holiday. Memorial day is celebrated the last Monday of May each year and commemorates (remembers and shows respect for) Americans who have died while serving in the military (being soldiers).
This holiday began after the American Civil War (1861-1865) to recognize and remember the more than 620,000 soldiers who died during the four-year war, which was considered the deadliest (causing death) in American history up to that time. After World War I, the holiday was expanded (made bigger) to commemorate all soldiers who died in military service.
To all those who have served and are serving in military service everywhere, we remember and honor you today.