Leading lines are a compositional technique used in photography to draw the viewer's eye towards the main subject of an image. 

These lines can be any visible lines or shapes within the photograph that lead the viewer's gaze towards the primary subject. The lines can be straight, curved, or diagonal, and can be created by natural features such as roads, rivers, or buildings, or by man-made objects like fences or staircases. 

Leading lines are typically placed in the foreground of the image and often start at the bottom or corners of the frame. By following the lines, the viewer's gaze is naturally guided towards the primary subject, which can create a sense of depth, perspective, and visual interest. 

To use leading lines effectively, the photographer should carefully consider the placement and direction of the lines, as well as the overall composition and framing of the image.