Original: The model was a successor to McDonnell Douglas's DC-8 for long-range operations, and competed in the same markets as the Lockheed L-1011 Tristar, which has a similar layout to the DC-10.
Simplified: The model was a successor to the company's DC-8 for long-range operations, and competed in the same markets as the Airbus A300, Boeing 747, and Lockheed L-1011 Tristar, which has a similar layout to the DC-10.