TTF is a file extension for a font file developed by Apple. TTF stands for True Type Font. TTF files are currently used by both Apple and Microsoft as a raster font format. As a raster font, it can be scaled to any size without quality loss or pixelation, and the stored image appears the same when printed as it does on-screen (see: what you see is what you print -- WYSIWYP).
The ability to view or use TTF files is embedded into Apple and Microsoft operating systems. TTF files can be created by image editing software, such as CorelDraw and OpenOffice Draw.