PWM meaning and modding cables

PWM means Pulse Width Modulation, and is a method of controlling fan speed. Typically fan speeds are dictated by the outright voltage supplied to it, if its on 6v its running half the speed if it were at 12v. PWM has a variable voltage, oscillating between 0 and 12v. If you want it to go faster, the higher voltage time of the "pulse" is elongated, vice versa if you want to go lower. In general its just a more accurate way of controlling fan speed.

Modding cable, not sure what you mean by this. Are you asking about sleeving?