Geographically, Earth is diverse. It has forests, deserts, mountains and seas. It even has polar ice caps, which is apparently an achievement considering the place is so damn warm now.
Earth has many diverse countries and cities, each with their own unique take on architecture, culture, lifestyle and transport. All of them have contributed to the growth and eventual expansion of Humanity as a whole, even North Korea. Earth also has one Moon, Luna, which is loved by Humans because of its silver colour.
Earth is protected by a network of Orbital Defence Platforms, like Cairo Station. These were set up during the Human-Covenant War and remained there until the Fall of Lord Hood. After the Empire of the Hood was destroyed, Humans had to be evacuated from Earth on board the Axiom whilst a cleanup operation took place, which ended up taking 700 years. This period of Earth history is known as The Great Exodus.
When Humans eventually did return to Earth, they found that nature had reclaimed the majority of their planet and they had to establish small colonies around the continents. After that, the population on Earth was strictly limited and property prices rose dramatically, so only the super-mega rich could live on the surface of the planet.
Despite this, the Earth remained well-loved by Humans for millenia to come and even after it was eventually abandoned and donated to the National Trust, the Earth was still a popular tourist spot due to the view from the windows of the space hotels in orbit. After its destruction in the year 5,000,000,000 PLF, the Human race decided to found New Earth, for nostalgic reasons.