Rack and pinion basicaly control your steering. You turn the wheel, a pinion gear at the end of the shaft moves the rack gear turning your wheels left and right all assisted by hydraulics. Probably best to get it repaired if possible or replaced.
As for the control bushings I've never heard them pop before. Squeak yes, clank from wear yes...but I've never personaly heard them pop. Not to say that it cant happen though.