There are 4 main types of tea, white, green, oolong and black tea.
White teas is the buds and young leaves from a tea tree which are Steamed then dried.
Green tea uses mature leaves which are then withered, steamed and then dried.
oolong tea uses mature leaves which are withered, bruised, partially fermented, panfired and then dried.
Black tea again uses mature leaves, its withered, rolled, fermented, fired and then dried.
You common or garden tea (PG tips and the like) is black tea.