Imagine a really big circle going all the way around the world called a "meridian." This circle helps us locate points on Earth and is used in maps and navigation. The 10th meridian east is a specific imaginary line that runs up and down the world, from the North Pole to the South Pole, passing through different countries and continents. It's called the "10th" meridian because it's 10 meridians away from the "prime meridian," which is the most important meridian because all other meridians are measured from it.
The 10th meridian east passes through several countries such as Algeria, Niger, Nigeria, Cameroon, and the Central African Republic. If you think of the world like a big pie, the 10th meridian east is like a slice that cuts through those countries. It helps people know exactly where they are on Earth and is important for things like air and sea navigation, as well as making maps. So, the 10th meridian east is really helpful to know if you want to understand how to navigate and find places all over the world.