Anti-roll bars are fitted across the underneath of the car, front usually and sometimes rear as well rear, joining the suspension units at each side. These help reduce body-roll in cornering and sharpen up the steering.
The bushings are rubber or polyurethene mounts encased in metal that hold the anti-roll bars to the car. The bushings, depending on the car, cost anywhere from €15 / €25 each (but you should fit them in pairs) and the labour charges would be anywhere from 1 to 2 hours.
You may need to have tracking and alignment work done especially if some chancer has tried it while the worn bushings were fitted.