Quantum chromodynamics (QCD) is a quantum field theory describing the strong nuclear force, one of the four fundamental interactions of nature. This force is responsible for binding quarks together to form hadrons, such as protons and neutrons, and for binding these hadrons together within the atomic nucleus. The theory posits that quarks carry a type of charge called "color charge," which comes in three varieties, and the mediating particles of this force are called gluons. QCD is characterized by a unique property known as asymptotic freedom, which predicts that the strong force between quarks decreases significantly as the distance between them decreases, allowing them to behave almost as if they were free particles at extremely short distances. At large distances, the force increases, effectively confining the quarks and ensuring that they are never observed in isolation.