Portage is a payment, usually to the captain or owner of a boat, for carrying cargo. A portage is also a bridge between two waterways.
A business that sells goods to many parts of the world will probably pay portage at some point: a fee to a boat for carrying cargo. This is a bit of an old-fashioned word, and it mainly applies to boats (which you can remember from the word port: a place where boats dock). Also, a portage is a bridge-like track built on land that links waterways such as rivers. The purpose of that portage is also to transport goods.