The terrestrial planets (Mercury, Venus, Earth, and Mars), also called the inner planets, occupy the region within 1.5 AU from the Sun. They exhibit manifold properties of their surface landforms, geology, interiors, and atmospheric features. The Earth possesses a unique nature; the natural conditions of our neighbors Venus and Mars are completely different. These two planets serve as two extreme models of the Earth’s evolution. Plausible scenarios of how these planets evolved and came to their modern natural conditions are discussed in detail.