The drivebelt they're talking about will be the fan belt to use the old term also known as the accessories drive belt, the serpentine belt (or simply the S belt). They drive the alternator, water pump, power steering pump and A/C compressor. Google serpentine belt diagrm and you'll find plenty.
They might/should run the engine briefly without the belt(s) fitted to see if the noise disappears. It's quite possible it's a noisy tensioner pulley bearing but it could also be an alternator bearing, noisy water pump, power steerig pump or A/C compressor. The alternator also has a clutch/freewheel mechanism in the pulley that can be noisy. They should be the experts to diagnose what or where the noise is coming from. Edited by: Victor
2015 Antara Exclusiv 2.2 163ps Manual 2WD