Earth is a rocky planet orbiting the Sun, the third from its star. In the mid-21st century, Earth was devastated by a blight that threatened all life. NASA launched the Endurance spacecraft through a wormhole in an attempt to find a new home for humanity. The planet was ultimately saved by the crew of the Endurance, particularly through the efforts of Murphy Cooper.
It’s reasonable to speculate that Earth didn’t survive the blight. The fact that Cooper Station orbits Saturn, and comments about Murph transferring from another station and being in hypersleep for two years, suggest humanity relocated to space, as Earth could no longer sustain life.
In an early 2008 script version, the story took a different turn. In the year 2320, Cooper returns to Earth in a Chinese spacecraft. The planet is a frozen wasteland, and he releases a fractal lifeform that thrives in the new environment. He then realizes the mission wasn’t about saving humanity, but about saving these alien creatures whose planet was doomed by Gargantua. He returns to the spacecraft, loses consciousness, and awakens on a space station orbiting Earth named “Space Station Joseph A. Cooper.”