What was the meaning of a multifront war for the United States during WWII?

The United States during WWII were simultaneosly fighting in two different fronts. The forces were splitted. On the first hand, they were fighting in the Eruopean front against Germany and the Nazis and, on the other hand, they were fighting in the Pacific, were there were several fronts both in Asia and in the Pacific Ocean, against the Empire of Japan.