I've been reading a lot and also been advised to place a series resistor (order of 33 - 45 ohms) on outgoing signal lines. Also called a termination resistor I believe. Example on this topic: Series resistor on digital signal lines
I'm wondering, what is the electrical aspect (theory) behind the resistor making the edges less 'peaky'. And also, it has been mentioned it is important to place the resistor as close as possible to the driver of the signal. What will change, and why, if it will, for instance, be placed more on the receiving side? (in case of a PCB that has no resistor on the driving side, will adding one on the receiving side make any difference?).
I could have responded to those topics but I thought a new topic for this particular discussion would fit better.