A quark is a subatomic particle which makes up protons and neutrons. There are three in each of these, there are also other particles (called mesons) which only have two. Quarks come with three different types of charges:. 1. The electromagnetic charge: same as electricity, quarks can have a +2/3 or -1/3 charge. 2. Chromodynamic charge: a "charge" (not electrical) described as "color" (for lack of a better term, they would actually look the same if you could seem them). These "colors" are red, blue, green, anti-red, anti-blue, anti-green.. 3. Another charge described as "flavor" (once again, not a true flavor). These "flavors" are up, down, top, bottom, charm, and strange. . The color charge has no connection with the electrical charge, but the flavor charge has a specific electric charge (up will be a +2/3 quark, down will be a -1/3 charge, for example).. Quarks cannot exist on their own, they must (color-wise) make "white", either by having a red, blue, and green together (as is the case with protons and neutrons), or a color and it's anti (example, red and anti-red, which are found in mesons). The colors are in a constant state of flux, and the color charge is carried between the three quarks by way of particles called gluons. A residual effect of the gluons (incidently, gluons carry something called "the strong force", one of the four primary forces of the universe) is to bind the protons and neutrons in the nucleus of the atom together.. Another force, called "the weak force", can cause quarks to change flavors (which usually causes them to change electrical charges), which means a proton can turn into a neutron, or vice versa. This causes beta decay, one form of radioactivity.. Kind of off-topic, but the other two forces of nature are electromagnetism and gravity.