A GLIF file is a file saved in the Glyph Interchange Format (GLIF) used for defining font symbols. It contains a glyph, which includes the name, format version, glyph width, and the X & Y point coordinates that define the outline of the symbol. GLIF files are saved in XML format.
GLIF files are commonly found in .UFO files to store information about each glyph within the UFO font set. The files are located inside the "glyphs" folder in the UFO file. GLIF files typically are not removed from UFO files and are accessed when a program opens the UFO file, such as FontForge, RoboFont, or Glyphs. However, since GLIF files are saved in an XML format, they can be opened by a plain text editor.