This is a standard TrueType font format developed by Apple Computer in 1989. The advantage of TTF till now has been its high level of font display control right up to the pixel. It has a vector format so it’s easy to scale. Today TrueType is used in operating systems from Apple to Microsoft.
This is a format for storing raster and vector fonts created or changed in FontForge. By opening an SFD file in this program you can store it in any modern font format like TrueType or OpenType. SFD contains all the information about the point setting of each symbol created or changed in FontForge.