Quarks are elementary particles and fundamental constituents of matter, combining to form protons and neutrons, which make up atomic nuclei. They come in six flavors: up, down, charm, strange, top, and bottom, each with unique properties such as charge and mass. Quarks are never found in isolation due to a phenomenon called color confinement. Instead, they are always grouped in pairs or triplets, forming larger particles known as hadrons. The interactions between quarks are mediated by particles called gluons, which carry the strong force that holds them together within protons and neutrons.