That is an excellent question Darwin, I am assuming your talking about this one on the main page under "Support us for free"
"As an Amazon Associate we earn
from qualifying purchases. This
does not cost you a cent, but it
helps keeps the forum online."
Since you saw this and realised there was not much of an explanation to go with it, why not drop a PM on Anton to ask him about this and let us know just what purchases would apply...I order many, many things from Amazon as well so this would be a good thing to know and keep in mind when we order stuff.