Planet Earth is located in the so-called Goldilocks zone or the habitable zone. This means that our planet orbits around the Sun at just the right range to receive the perfect amount of the energy from the Sun to support the presence of liquid water. Since life is dependant on water this is one of the crucial factors for whether the planet can sustain life or not.
Venus orbits too close to the Sun, so it receives too much of the Sun's radiation and Mars, on the other hand, is too far away from the sun to receive the necessary amount of Sun's energy to sustain life.
