Difference between first order difference method and generalized difference method

The original model is different. Difference method is to transform the original model into a difference model, which is divided into first-order difference method and generalized difference method, in which the original model of the two is different, and the generalized difference method is a new method of numerical solution of differential equations. It has both the simplicity of the difference method and the high accuracy of the finite element method, and it also has good properties such as maintaining the conservation of mass.