This article is from the Amiga FAQ, by Ignaz Kellerer with numerous contributions by others.
1. Agfa IntelliFont (suffix: .type or .lib) is the native font format on the Amiga. You can use it in any application and it can be converted to the standard bitmap format using the system utilities `IntelliFont' (OS 3.x) or `Fountain' (OS 2.x).
2. Postscript Type 1 fonts can be used within many applications, it can be used in every word processor and DTP program. There are two versions of the Type 1 format: Binary and ASCII (suffix: .pfb & .pfa). The Amiga software uses the Binary format, but you can easily convert them with TypeSmith or some PD software products (z.B. PFB2PFA) . In Addition to the files mentioned above, there are the metrics files with the suffixes .afm or .pfm. They contain information about the size (width) of the letters and most programs expect this file to be in the same directory as the font file.
3. Postscript Type 3 fonts (suffix: .ps or nothing) are not often used on the Amiga, but some applications do support this font format (e.g. PageStream). There are also some download utilities from PD sources available.
4. Truetype fonts (suffix: .ttf) are not very common on the Amiga, there is one word processor supporting this format (Wordworth 3.0). Due to the lower quality of the format, Amiga users tend to use higher quality for their DTP, DTV and word processing... There are also two formats: Mac & Windows available. The Amiga software is able to use the Windows format.
5. DMF fonts is the privat format of PageStream (suffix: .dmf), since PageStream is the market leader in DTP programs on the Amiga, so this format is very common!
6. Bitmap fonts (suffix: .font and numbers in a directory by the name of the font, sometimes .otag when converted from IntelliFont) were used in the OS 1.x, but have been replaced by the superior IntelliFont Format in OS 2.0. Under 2.0 or higher you still are able to use the bitmap fonts for small sizes, but for printouts you should use the IntelliFont format or any other vector font format mentioned above.
7. Colour Bitmap fonts (same suffixes as Bitmap Fonts, but the numbers have in addition a C, e.g. 35C) are also very common on the Amiga, they are mainly used for DTV applications, like the Video Toaster and Scala.