How do exit polls predict which party may win before election results are out?

Survey agencies conduct exit polls by speaking to voters immediately after they have cast their ballots. Exit polls give an idea of who could win elections, but they can sometimes be inaccurate. For West Bengal, Tamil Nadu, Puducherry, Assam, and Kerala Assembly polls, predictions could start coming in from 6:30 pm today, when EC's ban on such predictions would end.