The importance of Hiroshima is that Hiroshima is a city in southern Japan. It was the city on which the United States dropped the first atomic bomb that was dropped on Japan during World War II. This bomb was dropped on August 6, 1945 from an airplane called Enola Gay that was piloted by Col. Paul Tibbets.
The use of the atomic bomb on Hiroshima was meant to convince the Japanese to surrender. However, Japan did not surrender until after another atomic bomb was dropped on the city of Nagasaki three days later.