Topic: Using Gems

Hi, sorry if this is a silly question but i'm a little confused as to the use of gems.  Are they just another form of a tarball?  Or can you literally download modules as gems and you dont have to extract them or anything you can just do something like

require_gem '/home/me/this_isnt_a_gem.gem'

and it'll just use that module?  Thats the impression i'm getting from reading around but i cant get it to work for the life of me :-/

Ultimately, i'm trying use the id3lib ruby module through my home directory because i'm using it on a server where i dont have permission to install it into the native directory of ruby.  If theres some other way to do it, can someone please give me a quick tutorial?  I've been working on it for a few hours and kind of lost :-/.