Being front-line staff they are most likely to detect and stop fraudulent transactions in order to prevent losses at a bank (counterfeit currency and cheques, identity theft, confidence tricks, etc.). The position also requires tellers to be friendly and interact with the customers, providing them with information about customers' accounts and bank services.
Tellers typically work from a station, usually located on a teller line. Most stations have a teller system, which includes cash drawers, receipt validator/printers, proof work sorters, and paperwork used for completing bank transactions.