Concepts inRemark on “Algorithm 573: NL2SOL—An Adaptive Nonlinear Least-Squares Algorithm”
The method of least squares is a standard approach to the approximate solution of overdetermined systems, i.e. , sets of equations in which there are more equations than unknowns. "Least squares" means that the overall solution minimizes the sum of the squares of the errors made in the results of every single equation. The most important application is in data fitting.
more from Wikipedia