Urantia is the name used by celestial personalities to refer to our world, the planet commonly called Earth. In the larger cosmology of the universe, each inhabited world is assigned a unique name, and Urantia is simply Earth’s designation within the records and administration of the Local Universe of Nebadon.
Urantia is known as a decimal or experimental planet, meaning it is one of the worlds where life is designed with a greater allowance for variation and developmental experimentation under celestial supervision. This results in a richer diversity of life and a more complex evolutionary history.
Urantia is also notable because it was the world where Christ Michael incarnated as Jesus, making it spiritually significant within Nebadon. His bestowal here brought deeper revelation of the Universal Father, the nature of divine love, and the brotherhood and sisterhood of all humanity.
If you would like, I can also explain why Urantia is considered a decimal planet, how it fits into the universe structure, or its role in the larger spiritual history of Nebadon.