All particles can be classified into two broad categories: leptons and hadrons. The main difference between the two is whether they interact through the strong interaction. Hadrons are particles that interact through all four fundamental interactions of nature, which include, strong, electromagnetic, weak, and gravitational interactions.
Hadrons, the strongly interacting particles, can be further subdivided into two classes based on their internal composition: mesons and baryons. Originally, mesons and baryons were classified according to their masses. Baryons were heavier than mesons, and both were heavier than leptons. Today mesons and baryons are distinguished by their internal structure. Baryons have masses greater than the proton mass. All hadrons are composed of two or three fundamental particles, which came to be known as quarks. A quark is always combined with one or two other quarks.
According to the original model proposed by Murray Gell-Mann and George Zweig in 1963, there were three types of quarks indicated by the symbols u, d, and s. These were given the arbitrary names up, down, and sideways (now referred to as strange). Associated with each quark is an anti-quark, which are the antimatter equivalents of quarks, opposite in electric charge. Later evidence allowed theorists to propose the existence of several more quarks: charm(c), top (t), and bottom (b). These six quarks species are paired with their “flavors”: up and down, top and bottom, and charm and strange.
A baryon is a "heavy" subatomic particle having strong interactions (a hadron) which either is a nucleon or can transform or decays into a final state of stable particles including a single nucleon plus eventually some additional electrons, photons, neutrinos and/or nucleon—anti-nucleon pairs. This definition is only suitable if the quality characterizing a baryon is conserved in all involved reactions or decays and this is made apparent introducing a baryon number, which is +1 for a baryon and -1 for an anti-baryon. Baryons also include hyperons, which are created in particle accelerators.
All observed baryons can be described as quark compounds containing three quarks or, for anti-baryons, of three anti-quarks. Some examples of baryons are protons which contains three quarks (u, u, and d) and neutrons, which also contain three quarks (u, d, and d). From the properties of quarks, it follows that all baryons made in this way have integral electric charge, half integer spin and baryon number +1 (quarks have baryon number +1/3). The possible combinations of higher baryon number are identified with the atomic nuclei, but it is not excluded that they could exist as bound quark states too. The proton has charges of +2/3e, +2/3e, and –1/3e. The total charge of the proton is +e. The neutron has charges of +2/3e, -1/3e, and
–1/3e. The total charge of quarks in a neutron is zero.
The rule you need to remember for baryons is...