According to the structure of the planet they are divided into terrestrial and Jovian. Terrestrial planets have a solid, rocky surface, are relatively high densities, slow to rotate, lack a ring, and have little or no satellites.
They include all inland planets: Mercury, Earth and Mars. Of these Venus, Earth and Mars have atmosphere, while Mercury is practically gone. It is so thin that we cannot speak of it in our earthly sense.
The Jovian planets are similar to Jupiter. They are gaseous gins composed mainly of hydrogen and helium, they are low in density, have fast rotation, rings and many satellites and probably a little solid core. These are Jupiter, Saturn, Uranus, and Neptune.
Oftentimes it is "removing barriers to trade" that motivates countries to join regional trade blocs, since members of such "blocks" have completely free trade with one another.
