Hi Eddy!
Sorry my English isn't so good but I'll try to explain.
A soundfont is a soundbank, it's a collection of 1 or more sound(s) (instruments) in 1 file.
You can compare it to your keyboards Wave ROM.
You can make (sample) your own soundfonts by using programs like Vienna Soundfont Studio, but you'll need a special soundcard from Creative (A Soundblaster Live! or Soundblaster Audigy/Audigy 2).
A soundfont can be GM compatible.
So if you have a Soundblaster Live! for instance, you can download soundfonts from the web and load them in your pc's memory.
You can download an entire new GM set from the web, there are a lot of different soundfonts and have different sizes, there are GM sets that are only 512 kb's, but there are GM soundfonts that are pretty huge, like Fluid3, it's 147 MB!!!.
Although I think most of the free soundfonts don't have high quality sounds, there a few good ones.
For instance the ProTrax Classical Guitar Soundfont is amazing (Sounds like the megavoices of the Tyros).
And Fluid 3 has a pretty good piano sound.
Here are some links:
www.soundblaster.com www.hammersound.net http://www.thesoundsite.net/ Greetz,
Marcel