AFM (Adobe Font Metric): File name extension for a text file containing font metrics (character widths, dimensions, kerning, etc) for a PostScript Type 1 font.

ATM (Adobe Type Manager): Software for the Mac and PC that interprets Type 1 PostScript fonts and displays them on the screen instead of the system bitmap fonts. Unlike bitmap fonts, ATM font characters are vector based so they are smooth at any size.

BinHex: A type of file encoding that puts the Mac resource and data fork together in one file. It was originally used to telecommunicate files since both forks had to be transferred over a single ASCII text data stream. The Mac specific file type, creator and other information is also saved.

Bitmap Font: A font with characters represented as bitmaps or rendered images. The characters are not meant to be scaled. Scaling the font gives a blocky or jagged appearance.

CFF: Compact Font Format. Used in PostScript and some OpenType fonts.

DMG: Macintosh disk image. This is a file containing a representation of a Mac disk volume.

Encoding: A font encoding table associates character glyphs with index numbers. Changing the encoding changes which glyph is displayed for a particular key on the keyboard.

FAT: A file system used in DOS and Windows. FAT16 and FAT32 are variations allowing larger file system capacity.

FOND: A Mac FOND resource associates several fonts into a font family. It contains the menu name, metric information (widths, kerning, etc.), and a list of the associated fonts.

Font Family: A collection of several variations or styles (regular, bold, italic, etc.) of a particular font. Usually the font menu of an application will display only a font family name, then the user can select each style from a separate style menu.

Fork: A fork is a set of data associated with a file name in a file system. Macintosh HFS/HFS+ files can have two forks. PC FAT and FAT32 files have one fork. NTFS files can have many forks.

Glyph: The image of a character in a font.

HFS (Hierarchical File System): An older file system format used in the Macintosh.

HFS+: The latest file system for the Macintosh. Also called Extended file system. It can be larger and store files more efficiently than the older HFS version.

HQX: File name extension for a BinHex encoded file.

INF: File name extension for a text file containing individual platform, application and other metric information for PostScript Type 1 fonts.

Kerning: Individual adjustments to the space between character pairs that look too far apart or too close together. Kerning can make text easier to read by giving it a more uniform appearance. Tracking is similar to kerning but it is a spacing adjustment applied universally between all characters in a font.

Mac Creator: The creator is a unique four character signature identifying a program on the Mac. Each file associated with a program contains the programs signature which allows the Mac OS to launch it when those files are clicked.

Mac Type: The type field of a Mac file is a four character signature that identifies what type of information the file contains. It allows programs to show only files of a certain type in their open dialog boxes. It can also associate an icon for the file if none exist in its resource fork.

MacBinary: A type of file encoding that puts the Mac resource and data fork together in one file. It was originally used to telecommunicate files since both forks had to be transferred over a single data stream. The file type, creator and other information are also saved.

Multiple Master Font: An Adobe format. Multiple Master fonts can create many  font variations from a single base design.

NTFS: Windows NT file system.

OpenType Font: An extension of the TrueType format and was created to add advanced typography features. It also bridges the gap between TrueType and PostScript fonts by allowing PostScript style outlines (CFF).

OTF: File name extension for an OpenType font.

PFA (Printer Font ASCII): File name extension for a PC Type 1 font file (PFB) in ASCII text readable format.

PFB (Printer Font Binary): File name extension for a PostScript Type 1 font file. It contains font outline data in binary format. The PFB and an associated PFM file are used by ATM on a PC.

PFM (Printer Font Metric): File name extension for a Printer Font Metric. Includes much of the same information as the AFM file, only in binary format. ATM and Windows use this information for placing characters properly.

PostScript: A page description language (programming language for placing text and graphics on a page). Type 1 fonts are the native font format for PostScript.

Resource Fork: The PC and Mac differ in the way they store files. On a Mac each file can have two parts called forks. The data fork holds data (text, images, etc.). The resource fork holds resources (icons, fonts, menus, sounds, etc.). There are actually two files linked to one name in the file system. PCs only have one file linked to each name.

Tracking: A spacing adjustment applied universally between all characters in a font.

TrueType Font: This is a vector font format natively supported by both Macintosh and Windows operating systems.

TTF: File name extension for a TrueType font. This is a file containing font outline data in TrueType format.

Type 1 Font: This is a vector font format natively supported by PostScript.

Type 3 Font: These are actually PostScript programs which require a PostScript interpreter to display them. They are not compatible with ATM.

Vector Font: Fonts that contain instructions for building outlines from lines and curves which are filled to create the solid shapes of letters and other glyphs. The benefit of representing shapes this way is that they can be scaled to virtually any size and still retain smooth edges (unlike bitmap fonts which exhibit jagged edges when enlarged). Vector formats include TrueType and PostScript Type1 fonts.