Quarks are fundamental particles which have never been identified in isolation, and are only found as hadrons, held together by the strong force.
There are 6 types of quark: up, down, strange, charm, top, and bottom.
All quarks have a corresponding antiparticle, called an antiquark.
Quarks possess various properties, including having masses, charges, spins and undering both strong and weak interactions.
Quarks are not fully charged, but have fractional charges, -1/3 or 2/3, depending on the type. Down, strange and bottom type quarks have -1/3e charges, making them down-type quarks, whereas up, top and charm quarks have 2/3e charges, making them up-type quarks. Baryons (qqq) or mesons (qq-), are composed, so that each combination of quarks in a baryon form a interger, but combinations of quarks in mesons leads to interger charges. Baryons can be made with many combinations of different quarks, whereas mesons are made of a particular quark and it's constituent antiquark. Antibaryons can also be formed, using three antiquarks.