What is the difference between India ETA, Visa on Arrival, and a traditional India Visa?

All visitors to India are legally required to hold a valid visa to travel to India. Eligible citizens traveling for leisure/tourism purposes have the option to apply for an India ETA visa online, an electronic visa. On the India application form this is referred to as 'Visa on Arrival' because the traveler's biometric information will be taken at the airport and the visa stamped inside the passport upon arrival in India. However, it is very important to know that the ETA must still be issued in advance of departure, the process cannot be done on arrival in India.