There are four terrestrial planets in our solar system, and billions of them are outside our solar system.
Terrestrial planets are made of rock and silicate around a metallic core.
Earth is the largest terrestrial planet in our solar system.
NASA estimates that there could be more than 10 billion terrestrial planets in the Milky Way.
However, just because a planet is classified as terrestrial, it doesn't mean that it's necessarily habitable.
For example, in the solar system, Mercury and Venus are too hot for life to thrive, and Mars is likely too cold.
Apart from this, Mercury and Mars do not have a protective, breathable atmosphere like Earth's, and Venus has an extremely dense and toxic one.
Outside of the Solar System, Kepler-10b was the first confirmed terrestrial planet discovered by the Kepler Space Telescope.