Earth is the third closest planet to the Sun and is the densest and fifth largest planet of the eight planets in the Solar System. Earth is also the largest of the four terrestrial planets in the Solar System. Earth is sometimes called the world or "Blue Planet".

The Earth formed about 4.54 billion (4.54×109) years ago through accretion from the solar nebula. The release of volcanic gases is thought to have created an old atmosphere that was nearly devoid of oxygen and toxic to humans and most living things today. Most of the Earth's surface is melted due to extreme volcanism and frequent collisions with other celestial bodies. A major collision is thought to have caused the tilt of the Earth's axis and produced the Moon. Over time, the Earth cooled and formed a solid crust and allowed fluids to create on its surface. The first life forms appeared between 2.8 and 2.5 billion years ago. Photosynthetic life emerged about 2 billion years ago, enriching the atmosphere with oxygen. Most living creatures were still small and microscopic, until finally complex multicellular living creatures began to emerge around 580 million years ago. In the Cambrian period, Earth experienced a rapid, massive diversification of phyla.

Biological and geological changes have continued to occur on the planet since its formation. Organisms are constantly evolving, changing into new forms or going extinct as the Earth changes. The process of plate tectonics plays an important role in the formation of Earth's oceans and continents, including the life within them. The biosphere has a major impact on the atmosphere and other abiotic conditions on the planet, such as the formation of the ozone layer, the proliferation of oxygen, and the creation of soil.