Quick Answer
Voltage: 230V @ 50Hz.
Plug Types: Type C (Europlug), Type D (Old British 3-pin), and Type M (Large
South African).
Need a Converter? US/Canada devices (110V) need a voltage converter unless they
are "Dual Voltage" (Phone/Laptop chargers usually are). UK/EU devices just need a plug adapter.
Which Plug Adapter to Buy?
Buy a Universal Travel Adapter with surge protection. India uses a mix of sockets. The most common is the handy two-pin Type C socket found in Europe.
Power Surges
Power fluctuations can happen in India. It is highly recommended to charge expensive laptops via a surge protector or a good quality power bank, rather than plugging directly into the wall in cheaper hotels/hostels.