Basically, a no-load pot is a pot that, when at 10 or full up, 'removes itself' so to speak from the circuit completely by having a complete break in the tone circuit.. One way to achieve this is, like in the tutorial on the PG site, to scrape off some of the resistance strip inside the pot.. That way, when you turn the tone pot full up, the 2 terminals connected to the rest of the circuit (the negative and the middle usually) are not electrically connected in anyway...
Let's say you've got a normal Strat wiring.. Your tone pot should be wired at the middle and negative terminal with the negative terminal going to ground.. Ideally, when the pot is up all the way, there should not be any current flowing from one terminal to the other.. In reality, there is.. This causes some loss of treble in your sound..
A no-load pot creates a break in this circuit so that no signal flows through the pot to ground at all.. Effectively, this brightens up your tone..
Oops.. Forgot to add:
Linear pot: The resistance increases linearly as you turn the wiper..
Audio/taper pot: The resistance increases logarithmically as you turn the wiper..