The other, API, is a set of REST API methods.They can be roughly divided into two groups. The methods belonging to a first group are used to organize the payment process, i.e. accept shoppers' transactions. The Cashier widget is based on them (see "Cashier initialization" and "Payments" in the following figure); and you too can utilize them to connect your own front-end part if, for any reason, our Embed solution is not suitable for your business (see "MPI"). The methods belonging to the other group are intended for "after-payment" services: refunds and payouts.