Quarks are thought to be elementary point particles like leptons with no internal structure but unlike other particles have fractional charges.
Each quark has got either positive or negative charge equal to fraction Of an electrical charge and is assigned a specific quantum number.
Original three quarks were labelled as up(u) ,down (d), and stange(s), along with their antiparticles, and later on three more quarks along with their antiparticle namely charm (c),bottom (b) and top(t) were introduced.
The particles which you do not respond to strong interaction, but respond only to weak interactions and electromagnetic interactions are called as leptons.
They are all fermions of spin 1/2 and have a mass lesser than that of nucleons.
Members of this group are neutrino, antineutrino, electrons, positrons and muons.