The inner zone closest to the Sun contains rocky planets, known as terrestrial planets because of their comparative relationship to Earth A[...]
The terrestrial planets in this solar system occupy a habitable zone, defined as the region around a star that has conditions conducive to life as we understand it. Fundamentally, this means that the region has at least some planets with temperatures high enough to maintain liquid water. Of course, Earth is the only object in our solar system in this category but evidence supported the theory that Mars once had liquid water a well. Accordingly, the planets in this zone have long been viewed as possible abodes of life and were early targets for exploration because of this and because of their relative closeness to Earth. All have been visited, some of them many times, and the findings from the scientific investigations have both dashed hopes of finding life and of opening other possibilities for exploration.
Beyond the orbit of Mars but inside the orbit of Jupiter lies the main Asteroid Belt, consisting of thousands of rocky and metallic bodies. The total mass of this material is a small fraction contained in Earth's Moon.
Source: https://launiusr.wordpress.com/2016/03/18/three-zones-of-the-solar-system/