no-mod patches?

[zugz]

ok, simply put, what are these?
if you don't know what i'm talking about go over to megagames.com and check out their ps2 patches. well in there they have a few games that have no-mod patches available.

can someone tell me what these are? do they actually do what they say and allow you to play it w/out a modchip? if so, could you please elaborate on the proper way to do this

thanks

edit - not many games have this, only a few (Giants Citizen Kabuto is one)