A Channel is a static cryptocurrency address that may be assigned to each one of your customers.

curl -X POST \ \
-H 'Authorization: HMAC ***' \
-H 'Content-Type: application/json' \
-H 'Date: Tue, 19 Mar 2019 10:11:40 GMT' \
-d '{"pay_currency":"BTC", "receiver_currency":"EUR", "name":"channel name", "custom_id":"631044494"}'

They can send cryptocurrency to these addresses and it will be automatically exchanged into Euro or other fiat currency of your choice.

The customer can re-use this address, which is highly convenient - they can deposit funds without going to the cashier, or even logging in.

The trade-off with this approach is that customers receive the exchange rate at the moment transactions get confirmation on the network, not when they first send them. They may receive slightly more/less if the price moves dramatically over this period.