Pigeon VoIP is a technology that allows users to make voice calls over the internet at low rates, converting voice into a digital signal. With Pigeon VoIP through MTNL, users can call other VoIP users for free or make international calls for Re. 1 per minute. All that is needed is a broadband connection, telephone, and ATA box. Pigeon VoIP offers advantages like low costs, high quality calls, and ease of use across long distances.