Simplify Contour > Simplify attempts to streamline your outlines by removing unnecessary nodes and adding new nodes to the extrema, where required. It will do so by approximating a segment of the contour with a curve. It is different from Clean Up because it not only removes nodes, but can also add nodes; and because it is more aggressive and can make a more noticeable change in the contour shape.
This operation can be applied to a single glyph if it is open in the Glyph Window, or you can select several glyphs in the Font Window or Font Map panel and run the operation on all of them together. Apart from the Contour menu, this operation is also found in the Contour actions ==Tools > Actions=.
The good example of using this feature is in reducing the number of nodes after tracing a scanned image. Applying Simplify to this “D” glyph reduced the number of nodes from approximately 7500 to 2600: