Roughly speaking, an attractor is what the behavior of a system settles down to or that to which it is attracted. The attractor forms the limits of the pattern of the system. Imagine that you are taking the pulse, blood pressure and temperature of a person every hour, and you want to graph the relationships among all three vital signs as they change over time. You would construct a graph that was marked at the center by the intersection of three axes, one for each of the vital signs. Connecting these points in temporal sequence forms a trajectory. In nonlinear science, this trajectory is referred to as an attractor.