Imagine a really long time ago, when people didn't know that there was another side of the world. They thought that the world was flat and that if you travelled far enough in one direction, you would fall off the edge of the world.
But then, over time, people started to explore and travel more. They discovered that there was a huge body of water, called the Pacific Ocean, that stretched across a big part of the globe.
And as people started to explore and use the resources around the Pacific Ocean, they began to call this time period the "Pacific Century." It was a time when many countries, including the United States, Japan, and China, became very involved in the region, building things like trade routes, ports, and military bases.
During the Pacific Century, people started to realize how important the Pacific Ocean was to their economies and their ways of life. They also saw how the different countries around the Pacific could work together to solve problems and create new opportunities.
So, in summary, the Pacific Century is a time in history when people began to focus more on the importance of the Pacific Ocean, and how it could bring different countries together to create a better future for everyone.