# Trouble understanding Loop Filter in a PLL

I'm currently trying to understand the function of a loop filter. But where I'm stuck is that I know the output of the charge pump is a series of current pulses whose width is proportional to the amount of time that the there is mismatch between the reference and the VCO frequency. The problem I find is that each pulse can/should only occur at Fcmp right? So isn't it essentially just PWM? But at the same time, I've heard that the purpose of the loop filter is filter out jitter from the reference. But given that the frequency of the reference is pretty much fixed, I can only see it as an "integrator" or a crude A to D. So, I guess ultimately, what I'm asking is, what am I missing?