The four planets that orbit closest to the sun are best described as

Terrestrial planets

Explanation:

The first four planets which are closest to the sun are called as terrestrial planets. These terrestrial planets include Mercury, Venus, Earth and Mars. These planets are called terrestrial because they are earth like and are made up of either terrestrial substance such as rock, soil etc. or metals such as iron, manganese, etc. They also possess terrestrial features such as valleys, volcanoes and craters.