Originally posted by: Ell the Ewok
PiF is about sending people copies of something so that they can intern send it on to others.
This in theory helps the PiF system as more people have more DVDs and Projects to send on.

But Pay it Fowards means it's done without expecting anything in return, except that the people who get it do the same.

From http://en.wikipedia.org/wiki/Pay_it_forward: "paying it forward refers to repaying the good deeds one has received by doing good things for other unrelated people."