What does it mean that the photo is tangent to itself?

Screen capture visual effect brought by the line itself. According to the query of international tourism photography network, cutting is cutting; Line means line and tangent, that is to say, line will bring the visual effect of cutting the picture. If this cutting line is on the neck or head of a person, it will have the effect of cutting the head and neck. The scenery in the photographic background overlaps with the subject. In order to make the photos more beautiful and highlight the main body, attention should be paid to avoiding the tangent in the photographic background when shooting.