This format was developed to simplify use of Type1-fonts in some software. It’s 8-bit and so it’s quickly processed by programs and it has a compact structure. PFB contains additional metadata. Besides the storage of system fonts, a good example of its use is its application in AutoCAD to create font files with compilation.
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.