Along with the two other single polynomial interpolation method, Direct and Newton’s Divided Difference, there is a 3rd way, which is based on a weighted average of
the function values for points in the data set. Lagrangian Interpolation uses a set of polynomials that weight the function values based on the relative distance from the target point to each other point.

Click here for lecture slides based on Kaw Chapter 5, Section 5.04