Its lovely to see a post like this. Your in for some big surprises.
Porting is basicaly getting the program(the .exe or .com file) that currently works on your computer to work on a different type of computer say an apple or a linux computer or even an x-box. In this instance we mainly talk about games being ported, these are often programs where the original developers(people who wrote the program) have allowed people to have the program source, rather than just a program that only one machine can understand, it can be changed so another machine can understand it. Programs where you can look at the source can be changed to run on the GP2X. Games like DOOM,Duke Nukem,Quake,Shadow Warrior,Marathon etc etc have there source available.
Not just games have there source available Video players, Text editors, DTP packages, have there source available, but most importantly for the GP2X some emulators are available to port.
An emulator is a program that does something very special, It gets one computer to petend to be another, so my GP2X can be a BBC,Neo-geo,Nes,Genesis,C64 or even a PC-engine. So while the program is running on the GP2X it is another machine. To petend to be another machine it has to be at least 12X as fast, most of the discussion that goes on here is whether it is fast enough to petend to be one machine or another. So you don't say what has been ported because the programs have not been changed they are still the same ones that worked with the original computer. So often In here we talk about compatability, thats how good a machine can petend(emulate) to be a another. The better it is at petending the more games work.
Both emulating and porting are different ways of getting, games that work on a different computer to work on the GP2X. Porting where the source is available, emulating where it is not.
Hope this has helped rather than confused, judging by your post you are in for a serious treat, and if anyone gives you any trouble, give it back