Here's why:

* Stars are much, much larger. Even the smallest stars, called red dwarfs, are significantly larger than Earth. They are about 10-20% the size of our Sun, which is itself about 109 times the diameter of Earth.

* Earth is a planet. It's a rocky body that orbits a star, while stars are massive balls of hot gas that generate their own light and heat through nuclear fusion.

While there are no stars the size of Earth, there are objects called neutron stars that are incredibly dense and small. Neutron stars are the collapsed cores of massive stars after they have exploded as supernovae. While they have a radius of only about 10-20 kilometers, they are incredibly dense, with a teaspoonful weighing billions of tons. However, even neutron stars are still significantly larger than Earth.