Does the receiver pays to get the package or just the sender has to pay to send it and that's that?

Don't no

If you are creating the shipment, you have to pay, otherwise the reciever would have to create the shipment online and send it to you via email. Unless you are using their account number.

I've had two international packages delivered there and as the receiver I didn't pay anything.

The sender and receiver need to work out those details beforehand.