Path of Exile is a free online ARPG game. It has a unique barter trading system, you can buy items for POE Orbs (premium, chaos, etc.) on the official trading site. The noble Chaos Balls are the most popular currency for trading or storing value in the game. They are the "gold" of POE. Balls can be used not only for trading, but also for crafts-you can easily use them to make sturdy objects.
Regarding POE Currency, my suggestion is to buy it on POECurrency.com, which is more cost-effective than slowly gaining in the game. Their website keeps a large amount of currency and item inventory in order to be able to deliver your order within half an hour. You can pay by phone, SMS, mobile phone, Paysafecard, PayPal, credit card, gift card, bank transfer, iDEAL, etc. After placing the order, their delivery team will contact you within a few minutes. Then, they will invite you to the party and enter their hiding place, and deliver your order through the transaction window. Fast and safe!