Inevitableavoidance:
Does the "33R" get the entire current from the led's through it?If so, i'll need a high wattage resistor for that, right?
Yes it does, you will need to work out how much power the resistor dissipates depending on the current, I squared R
i don't quite get what the schematic,
Think of it like this. The 33R resistor drops a voltage according to how much current is flowing. This in turn raises up the voltage on the emitter and throttles back the base current until an equilibrium is reached. If more current flows through the LEDs, because they heat up, then there will be more current through the 33R and the voltage across it would like to rise but this turns off the transistor a bit more and so in effect nothing happens.
The resistor is acting as a feed back mechanism for the transistor and thus supplying a constant current in the light of any changes in the load. The value of this constant current is controlled by the size of this resistor. You want more current, you make that resistor smaller so more current has to flow through it in order to develop sufficient voltage to throttle off the transistor.