The weeds won't grow through it. However, as dirt collects in the rock/gravel, they will grow on top of it. The good part is that they are very easy to pull since their roots are only down to the fabric. I put it down around my rhodies after I lay a soaker hose, then bark dust on top of the fabric. I still get occasional weeds in there after three years of dust blowing in, however they easily pull up so I'm still happy about it. The weeds that do start seem mostly not to last. I suspect it's because the top doesn't get water during the summer so only the hardiest make it until the end of June. :-)
I suspect raking the bark dust would have also eliminated any weeds growing as it would expose their roots to the sun.
The good thing about is if I ever want to get rid of it, it will be only the two pieces I put down to remove, not the jillions of pieces of black plastic I had to clean out of the flower beds when I moved here!
Where we put it on the RV pad in the back has little vegetation. When I bought this house, that area was a 12-plus-foot high bunch of Himalayan blackberries. We used a backhoe to dig them out and also hauled off extra dirt to help ensure getting most of the roots. I then violated a basic belief of mine and we added casaron (?) to the area (the only poison ever in my yard), covered it with fabric, then the gravel. That was in 1999 and all is still in good shape, little vegetation and all the gravel still in place. However, it doesn't get a lot of traffic.
This morning, I pulled up some fabric that I had covering the yard by the driveway that I didn't want to deal with. There were occasionally a series of roots that were growing all around trying to get through. It was actually quite funny. The weeds that were growing on the top there were already dried for lack of moisture so were easy to pull off with no root depth. Actually, it was a bit weird. LOL
Glenna