This is useful when you are animating a model and you can’t easily subdivide the simulation geometry. Often, the geometry that’s used for rendering the cloth is not very suitable for simulation purposes. The number of polygons in the rendering geometry may be too high, and the shape of the polygons on the mesh may be ill-suited for nice looking simulations.
Using Cloth Proxy
Click the Cloth Proxy tool on the Cloth tab.
Select a the geometry object to deform with simulated cloth and press Enter to complete your selection.
Select the simulated cloth object to use as a deformer and press Enter to complete your selection.