What is to: ferrying to buoy and back

I believe it means to paddle sideways to crow a channel or river or simply meet at a certain point while avoid being taken over by a current. Could somebody clarify?

Are you asking what is “ferrying”?

yes basically
when I hear ferrying to a buoy it’s generally in the context of training or practice to see how accurate you are at setting a good ferry angle. The strength of the current vs your own strength dictates how much you aim more upstream or more cross stream such that you basically don’t move much relative to the river bank (or coast in a tide race) and cross the current. You also avoid positioning yourself such that the current slams you into the buoy.

In a simple ferry, you point the boat into the current with a slight angle and move sideways without moving upstream or downstream much. The trick is to keep the current from turning you downstream.

You can also back ferry with the stern pointing upstream using backstrokes. Ferrying is a good skill to have in any moving water and starts to become important on many Class III creeks.