An Earth-like planet is a planet that shares similar characteristics to Earth, such as a solid surface, liquid water, and a suitable atmosphere for supporting life.
The key factors that make a planet Earth-like are its size, distance from its star, and composition. A planet should be in the habitable zone of its star, have a solid surface, and have liquid water on its surface.
It is estimated that there could be as many as 40 billion Earth-like planets in our Milky Way galaxy alone. This suggests that Earth-like planets may be quite common in the universe.
It is possible for an Earth-like planet to exist outside of the habitable zone, but it would require some other factor, such as a strong greenhouse effect, to keep the planet's surface temperature suitable for life.
Some of the challenges of finding and studying Earth-like planets include their small size and distance from Earth, making them difficult to detect. Additionally, distinguishing between habitable and non-habitable planets can be challenging due to limited data. It also requires advanced technology and techniques to study these planets in detail.