The Earth is a big round ball called a globe. People use lines to help them find places on the globe, and the 100th meridian east is one of those lines. We call it a meridian because it goes from the North Pole to the South Pole, and it helps us measure distances east and west around the globe.
So, imagine a big imaginary line that goes straight up and down on the globe. If you were standing on that line, you would be exactly halfway between the two poles. That line is the 100th meridian east.
Now, when we talk about "east" and "west" on the globe, we mean the direction you move when you travel from one side to the other. So, if you were standing on the 100th meridian east and started walking towards the east, you would be moving further away from Europe and Asia and closer to Australia and the Pacific Ocean.
The 100th meridian east also happens to be an important line for understanding weather patterns in the United States. To the east of that line, there is usually more rain and humidity, while to the west of that line there is usually less rain and more dryness. This can make a big difference for farmers and other people who depend on the weather to make a living.
So, in summary, the 100th meridian east is an imaginary line that goes straight up and down the globe, dividing it into two hemispheres. It helps us measure distances east and west, and is an important line for understanding weather patterns in the United States.