The slopefields activity allows you to plot a family of solutions to a single differential equation y' = f(t,y).  The slope of an arrow located at the point (t,y) is given by f(t,y) and indicates the trajectory of a solution to the differential equation through that point.  The slopefield of a differential equation gives useful information about the general trends and stability of the solutions.  You can resize the window using pinch and pull gestures as well as add solutions by tapping on a point within the graph.  Enter your own equation or explore one of the preloaded equations.