On Earth, the quarks that are commonly observed are up quarks and down quarks, which are the lightest and most stable types of quarks. These two types of quarks are known as the "first-generation" quarks. They combine to form protons and neutrons, which are the building blocks of atomic nuclei.
However, there are other types of quarks known as "second-generation" and "third-generation" quarks. The second-generation quarks include the charm quark and the strange quark, while the third-generation quarks include the top quark and the bottom quark. These quarks are generally less stable and are typically produced in high-energy particle collisions, such as those occurring in particle accelerators or during cosmic ray interactions.
While second-generation and third-generation quarks can be produced on Earth in certain high-energy experiments, they are not commonly found in the ordinary matter that we encounter in our daily lives. The up and down quarks are the dominant types of quarks in stable matter on Earth.