All the previous methods (Euler, modified Euler, Huen and Runge-Kutta methods) are called single-step methods because they use only the information from the last step computed.
Single-step methods – require information at a single point to find .
Multi-step methods – require information at more than one point to find . Utilize the past values of y and/or to construct a polynomial that approximates the derivative function, and extrapolate this into the next interval. The number of past points that are used sets the degree of the polynomial and is therefore responsible for the truncation error.