it's all explained in what they put in your passport. I have 12 years of volunteer visas and used to look after 170 volunteers for a foundation so I know a little bit if you need to know more.
It's a payment system allowing you to invoice clients and receive payments in USD, EUR or GBP, then you can withdraw local currency from an ATM wherever you are in the world.
There's so many features to assist your money tracking and making sure you get paid.