As explained in the TrueType and OpenType specifications, those tables (as well as the glyf table) contain hint instructions. The hints are what make a font look good at low resolutions. You can’t add hinting through FontCreator, but you can use FontCreator in combination with Microsoft Visual TrueType (VTT). VTT is a professional-level tool for graphically instructing TrueType and OpenType fonts. VTT It is free and can be downloaded from here:
http://www.microsoft.com/typography/DevToolsOverview.mspx
Manually hinting a font is not an easy task and takes a lot of time.
Another way to improve the quality at small sizes is grayscale support. To enable it select Grayscale from the Format menu. Delete all entries. Now add a new entry and set “Grayscale rendering”.
More about hinting:
Basic hinting philosophies and TrueType instructions
The raster tragedy at low resolution
Font Hinting and Smoothing