Quarks are elementary particles that form matter. They are also fundamental particles or constituents of matter. When they combine, they form what is known as hadrons. Examples of hadrons are neutrons and protons.
Quarks don't exist in isolation as they are always in a combined state, particularly within hadrons. It is important to note that all observable matter consists of a combination of up quarks, electrons, and down quarks. For instance, it would take one quark down, two up quarks, and the glutons to have a proton. This tells you that all matter is composed of these elementary particles.
The interesting thing about quarks is that they all have color charge, electric charge, mass, and other intrinsic properties. There are about six different types of quarks, they include: strange, bottom, top, up, down, and charm, with up and down quarks having the lowest masses. Another name for all the six types of quarks is flavor.