There are six known types of quarks, often referred to as flavors. They are:
Up quark (u): The up quark has a charge of +2/3 and is the lightest quark. It is commonly found in protons and neutrons, which are the building blocks of atomic nuclei.
Down quark (d): The down quark has a charge of -1/3 and is the second lightest quark. It is also a constituent of protons and neutrons.
Charm quark (c): The charm quark has a charge of +2/3 and is heavier than the up and down quarks. It was discovered in experiments in the 1970s.
Strange quark (s): The strange quark has a charge of -1/3 and is slightly heavier than the up and down quarks. It was discovered in experiments in the 1960s.
Top quark (t): The top quark has a charge of +2/3 and is the heaviest of all known quarks. It was discovered in experiments at Fermilab in 1995.
Bottom quark (b): The bottom quark has a charge of -1/3 and is the second heaviest quark. It was discovered in experiments at Fermilab in 1977.
These quarks are the fundamental constituents of matter, and they combine in different ways to form composite particles such as protons, neutrons, and mesons.