* The 4 (four) rated questions *

 What is a Mod File?
    A mod is a music file format for which can be played by computers with a soundblaster or sound blaster compatible sound card. It contains several different   samples, or instruments, as well as a set of binary instructions (sort of like a program written by the composer) that tell the computer when to play each one, and at what pitch. This allows someone to take many different sounds and compose a song out of them.

 Which Platforms Support Mod?
   I would say most of the platforms used today. The MOD format was originally made for the Amiga, but is now widely accepted in the PC world because of the quality you can achieve with limited, standard hardware. Macs support it too.

 Do I need any special hardware or software to play modules?
  Not really, but you need a sound card capable of playing sound through a digital channel. SoundBlasters, or any Soundblaster compatible card fall into this catagory, as well as just about any sound card on the market (except old Adlib cards).

 How Can I Make My Own Mod Files?
  There are many different programs available for writing mods, they are called trackers. A tracker is to a mod, like a word processor is to a document. Almost all trackers are either shareware or freeware, and available over the internet. (see Beatmaster's Download area --> Programs for more infoz)
There are many formats that may be referred to as mods (.mod), i.e. Fasttracker II (.xm), ScreamTracker III (.s3m), MultiTracker Module (.mtm),  and a few others.