Baryons consist of 3 valence quarks and limitless numbers of virtual gluons and quark-antiquark pairs. Mesons consist of a bound state of a valence quark and antiquark, plus limitless numbers of virtual gluons and quark-antiquark pairs.  The spin of baryons and mesons is not intrinsic, but apparently a combination of spins and orbital angular momenta of the components of the system.  Since the binding energy of hadrons is infinite, there are an infinite number of different baryons and mesons.  Since almost all baryons and mesons are unstable, the familiar and fundamental relation ΔE Δt ≃ ℏ means that the unstable particles do not have definite masses.

The fundamental vertices of the Standard Model.  See the corresponding Wikipedia entry for an explanation of some of the notation used in this figure.  The Standard Model has 26 parameters (coupling constants, masses, etc.) but these are not free, they are fixed by experiment.  "Give me six free parameters and I can fit your grandmother!" -- John von Neumann.