The 'T-zone' on the face refers to:

The T-zone refers to the area across the forehead and down the nose and chin, which forms a 'T' shape and is often oilier than the rest of the face because it has more active oil glands. Combination skin is typically oilier in the T-zone and normal-to-dry on the cheeks. Recognizing the T-zone helps the cosmetologist analyze combination skin and tailor products to different facial areas. Knowing this common skin-analysis term is part of the esthetics fundamentals included on the exam.