PayTM stands for Pay through mobile. Paytm is an Indian e-commerce payment system and digital wallet company. It was founded by Vijay Shekhar Sharma in August 2010 and is based out of Noida, India. Paytm is available in 10 Indian languages and offers online use-cases like mobile recharges, utility bill payments, travel, movies, and events bookings as well as in-store payments at grocery stores, fruits and vegetable shops, restaurants, parking, tolls, pharmacies and education institutions with the Paytm QR code. As of January 2018, Paytm is valued at $10 billion.
***Disclaimer, I have read a lot about PayTM, and this answer includes excerpts from many people I talked to and even some Quora geniuses who took the time out to explain the model in deep! This post is a collection of information to present it to a broader audience!***
So let us see, why PayTM became so successful so fast! There are many things to learn from this post so take out your notepad and start writing this down!