"The Minister gives the Waste Advisory Board a list of tasks to work on."
The Minister tells the Waste Advisory Board what to focus on when giving advice under section 90. You know the Minister does this by sending a written notice to the Board. The Minister can change what the Board focuses on at any time by sending another written notice.
The Minister has to make sure the Board knows what it is supposed to be doing. You can think of it like getting instructions for a task. The Minister gives the Board its instructions, and the Board follows them.
If the Minister wants to change the instructions, you will know because the Minister sends a new written notice to the Board.