What separates terrestrial planets from Jovian planets is their composition. Earth and Mars are both examples of terrestrial planets, all of the planets in the inner solar system are terrestrial. Terrestrial simply means that the planet is made up primarily from rock, with little of the planet being atmosphere. Jovian planets, who get their name from Jupiter, are large gaseous planets. These gas giants have relatively small rocky cores, with tremendous atmospheres. Jupiter is so large, some of its moons could qualify as planets if they only orbited the sun instead.
Scientists have been discovering many new exoplanets thanks to new telescopes and refined technique. Due to size and gravitational energy, Jovian planets are much easier to find than terrestrial planets. The few terrestrial planets that have been discovered so far are exceedingly large for rocky planets and have been classified as super earths. Some of these terrestrial planets are as big or bigger than our biggest gas giant. A few recently discovered gas giants have been found to be possible failed stars.
Earth is the only known life supporting planet. Most scientists agree that life is more likely to exist on a terrestrial planet than on a Jovian planet. This does not mean life does not exist there, and life could very possibly exist on a large moon of a Jovian planet. The large gravitational field of large gas giants can cause the core of large moons to remain hot long after it should have cooled, providing energy for the planet. Typically a planet must be relatively close to its star to hold liquid water, the proposed basic building block of life.
Terrestrial planets are generally smaller than the Jovian giants. Jovian planets form further away from their star than rocky planets and are thought to be more suited for the evolution of life. Gas planets can have extraordinary atmospheric pressure, and can have a core big enough to be its own planet. Mercury, Venus, Earth and Mars make up the terrestrial planets of the inner solar system, while Neptune, Uranus, Jupiter and Saturn make up the gaseous outer solar system. Jupiter is alone several times larger than all of the terrestrial planets, and it’s magnetosphere is the size of the sun. The composition, size, location and behavior of terrestrial planets differes greatly from that of Jovian planets. These two planet types are the primary classifications for now, but new things are discovered everyday.