Earth orbits the sun at a distance of approximately 149 million km. Earth, the third planet from the Sun after Mercury and Venus, is the home planet of mankind.
It has a natural magnetic field (which Mars has not) that protects from solar wind. Earth is seen as a bright morning star from Mars. Earth has a mostly nitrogen atmosphere and has liquid water. The nitrogen might be the hardest element to obtain for the eventual Terraforming of Mars.
The population on Earth is around 7 900 000 000 persons, increasing exponentially. However the United Nations population projections mostly show a reduction in growth in the next few decades, peaking at about 12 billions. The is no sociology on Mars. Yet.