Quarks and Antiquarks are the fundamental particles.
They are what make up nucleons, i.e. protons and neutrons, as well as other particles.
There are 6 types of quark, of which two occur in protons and neutrons.
These are shown below in the examples. These quarks are known as UP (u) and DOWN (d).
They have charges of +2e/3 and -1e/3 repectively.
Nucleons containing UP and DOWN quarks
The 6 quarks along with their antiquarks, make up the quark family. The properties of antiquarks are similar to those of the corresponding quark, but with the opposite sign.