T-Zone - is the part of the face that is composed of forehead, nose, and chin, forming an imaginary letter "T". This area is known for concentrating most of the facial oiliness, because it has a high concentration of sebaceous glands.
It is a technique used to define the line of the eyeliner made in the make-up and, consequently, leave a well-defined production on the eyes. This technique consists in darkening the upper waterline, resulting in an elegant, highlighted look.