Poke coins are currencies in Pokemon Go game. These coins can substitute for purchasing items, upgrading permanent inventories or for limited use incubators. Poke coins can be availed from various places in the game and various activities such as
* Defending a gym
* Poke stop visits
* Buying using real world cash.
While first two steps are reasonable and effective, they might take long time for you to get all the items in the shop. Hence, if you want quick coins, you either have to pay real-life cash for buying coins or resort to quick-fix of unlimited poke coins that are available online.