A LineString is a one-dimensional object representing a sequence of points and the line segments connecting them. A line-string has a length but no area.

Figure 1 shows examples of line-string geometries, (1) is a simple, non-closed LineString instance, (2) is a non-simple, non-closed LineString instance, (3) is a closed, simple LineString instance, and therefore is a ring (4) is a closed, non-simple LineString instance, and therefore is not a ring.

Figure 1: examples of line-string geometries