The term 'Planet Earth' refers to our home - a planet in space that is inhabited by living organisms, including humans. It is the third planet from the sun and has an atmosphere that supports life due to its distance from the sun, which provides it with heat and light necessary for plants to grow. The Earth also rotates on its axis, causing day and night cycles, as well as having a moon that orbits around it. In summary, 'Planet Earth' refers to our home planet, where all life exists and thrives due to the unique conditions that make it habitable.